Error tracing and cleaning
had accumulated a long and hard life behind, for much dust and traces
of rust. The equipment serves as a spare part donor. It is actually
culpably equipment in such a way comes to leave. After cleaning a few
years can never harm.
amplifier is to be repaired. It still is in a tidy condition. Broken,
at the output stages the exit hangs firmly on +60 V. Without the
inserted protective circuit it would have been the end for a DC coupled woofer.
plate solder side. To their in the past clearly already one soldered.
To see down on the right of also the semiconductor cemetery, all
defective output stage transistors. With many a low impedance
connection between basis and collector. One thereby without
short-circuit, large currents
must have flowed.
The orginal output stage transistors are the PNP
types 2SA1065 and NPN types 2SC2489. Both are very fast, them are fast
bipolar power transistors (150V/10A/120W). Unfortunately all are
defective. A few new 2SC2489 and a set of 2SB681 PNP and 2SD551 NPN
(150V/12A/100W) are provided. At first sight these fit as replacement
quite well, the amplifier however not for these types were compensated.
If the original typ is
still available hardly, the usual transistor comparing lists help.
These lists do not beru-hit a corner-sight however always all
parameters. If another transitor type
is used, always exactly superior at which screw thereby one turns. In
many cases is it possible, often is even improvements thereby
attainable, in addition, the opposite is possible. The amplifier can
reciprocate and be able even still more semiconductor broken to go.
After the cleaning the printed circuit board is
again clean. To see on the right of and on the left of the TO-3
versions for the output stage transistors, which are put and over the
two screws the collector (housing) contacted. The put variant is very
low-maintenance. White resistances are 0.47 ohms of resistances, them
serve for the local inverse feedback and simplify also that join in
parallel the transistors. The driver transistors apparent get along with small
radiator box. Fortunately is present service the manual, without
connection diagrams would be the repair a toilsome work.
fast searches of errors in the circuit a simple circuit analyzer
thus the pns of transitions with for instance 600mV
at basis emitters and basis collector can be examined. Rough
Transitordefekte is so recognizable.
Diodes in passage direction show for instance
Resistances may be never many high impedance as the
nominal value, otherwise it is surely broken. Often the ohm measurer
shows however a lower value, is usually because of the parallel
connection with other elements. Many defective of resistances show
"become high impedance" up to the complete loss. The devil is however
in the detail, sometimes gauckeln the resistance condensers joined in
parallel the circuit analyzer wrong values forwards, it can several
seconds take to the announcement stands.
in the inserted condition DC voltage
measure. However the oscilloscope, it is clearly safer shows the cam
shape, the circuit analyzer is unsuitable in this relationship.
At first sight
- OK ONE - the output stage was attached now at will at the left
channel. It equipped with the provided 2SB681 and 2SD551 Transitoren.
Those are not the correct, but the only sentence, which are still
functional. For tests is correct even if it hops go could. Volume
controls on zero, entrances leave and power ON open. Often an
oscillation begins not immediately with the smaller amplitude to
reciprocate but only with larger - thus a small signal put on and volume slowly untwist
and at the oscilloscope observe which happened, if the sine begins
easily - danger! - can have gone to volume back - if the scope then becomes nevertheless
suddenly completely "green" is often too late it - the transistors
broken. The risk of an immediate oscillation exists.
Toshiba power bipolar transistors
in the TO-3 housing. Installed with thermal compound and mica
disks for the electrical isolation of the collector to the radiator
box. When the assembling of the insulating washers gladly errors are
made, therefore with the ohm meter for high impedanceness to examine.
The thermal compound is widerliches things at the fingers that then
later also everywhere at the whole table lubricates. Lay on only as
much that the surface scratches and unevenness in the insulating
material, housing and radiator box are filled out. The paste is not to
form an additional developing layer, which worsens the thermal
resistance, really only for gaps to fill. Also fully do not tighten the
screws at the beginning, so that few days later after the first
enterprise still a something can be pulled tight. It lasts always
something to itself the paste completely sets.
switching on on is the amplifier stably, off approx.. it begins to
reciprocate to 25 V easily. 2 kHz without load at the output.
Now if the
amplitude is still continued to increase (10V/DIV), the oscillation
begins, very clearly particularly in the negative half wave.
Transitoren became warmer, by the permanently flowing idle current. The oscillation grows,
slowly it off time will switch.
The causes for an oscillation
are variously, probable a defect in the first part of the output stage
(long plate behind the large electrolytic
caps). Whereby the wrong output stage transistors this
oscillation with to favour can.
Now an attempt
was started, as the last remaining 2SC2489 orginal transistors
affects the output.
times the oscilloscope exchanged one with CRT
readout. The picture shows the amplifier in the no-load
operation with PNP spare transistor and the orginal NPN in the positive
on 4 ohms a load the amplifier becomes stable. Only strangely enough it
already begins with approx.. to clippen -13 V. Still defects must be
Power Amp (X00-2010) part
Now it applies to examine the long plate behind the
In the long
printed circuit board (X00-2010) (B) directly behind the large caps very probably is an error. The
two channels are symetrically
developed, quite short layout,
hardly wire entanglement. The oblong, narrow, small Transitoren is
Doppelfet's in the first stage (for instance in the picture center on
the right of and left), in a housing that is favourably e.g.
because of the drift characteristics over temperature. Which with the
years, the decreased capacitance of the elektrolyt capacitors became possibly
critical. Also the small potentiometers (above) are gladly a problem,
only to turn if necessarily,
outside of the place where the middle
contact all the years is confessed, the surface are gladly
dirty, there must few times turn to become around the deposits with the
middle contact to
error already found, a 180 ohm resistance more largely than the
measuring range of 2 kOhm. That is broken. The surrounding construction
units, in particular semiconductors applies it now to naturally also
examine. Down with the printed circuit board, sometimes more simply
said than done. First a few pictures make, serves later than assistance
around to know which wire again where be rank-soldered must, without
studying laboriously the connection diagram. If the wires away are,
still the plastic tie-clips come.
became completely dirty with the years. Down one sees the four electric
rectifiers capacitors. In
the present condensers with same capacity became importantly smaller
and also better. Nevertheless I see no reason it exchanging with those
for the time being, am nearly still ok, am also not so cheap. Besides
also here something Orginalzustand is lost, although is rather all the
same to me otherwise actually. Measuring of the capacity would be
interesting, but only if they out-solder themselves
leave. Who does not have a capacity measurer
for high capacities, this can judge also in such a way: Amplifiers e.g.
with 4 ohms load (sufficiently strong loudspeaker goes naturally also),
to untwist times correctly. Observe a sine signal and the appearing ripple
voltage at the condenser with the oscilloscope as signal
source. With a bad capacitor
with falling capacity a high ripple
will anyhow have to be seen.
inhibitions, the dirt must simply down of the printed circuit board. A
mild seifenloesung makes nothing at all for the printed circuit board
and electronics. A cleaner is also favourably, since it dries
arrears-free and well, like the table-ware also. Of course also white
spirits go, are however already stronger in the effect, give gladly
easily matte of arrears on the printed circuit board and are the
recommendation for the second wash course. The spray "LR" printed
circuit board cleaner with plastic brush in the spray button
integrated, of the contact chemistry supplies good cleaning results.
For a strongly verdreckte plate one needs however much of it. LR is in
the best way suitable also for soldering arrears of all kinds. There
are possibilities a printed circuit board to be
It can already be that water is clean-run somewhere into a construction
unit, where it would when new not clean-run it a certain risk. A usual
construction unit that because of washing now accelerated broken would
go, soll's nevertheless calmly directly broken go, I remove
it, rather with me than in the next year with you in the living room.
the printed circuit board is drying to foehn, but not with the 2000
Watts, but like that that one can hold the printed circuit board
thereby still comfortably with the hand. Do not adjust thus too hot. A
compressed air pistol dries also well. Only at air to leave go also,
the landing on water esters dry, one do not see remaining however for a
very long time not receive, are not not so mad when switching on on. A
heating element does good services. Landing on water esters form e.g.
in the housings of the small potentiometers, these must in any case
have drained before switching on on. The cleaning already requires a
certain expert knowledge. A clean printed circuit board makes possible
also an optical inspection. Even if it does not harm functioned, it
these also under a magnifying glass to regard correctly. Fine tears in
the conductive strips are to be never excluded, and mechanically
damaged construction units better recognizably. Can the soldered
connection one so also better observe or after-solder.
circuit board (X00-2010) (B) looks now again clean. The remaining
defective construction units on this printed circuit board, Transitor
Q20, one NPN 2SC2633 and two pertinent of resistances R48, 50 with ever
180 ohms. In the other channel Transitor Q19 2SC2633 was
defective, but resistances the ok. Why also always the power stage transitors went broken, very probably a defect
caused the other one. By the one internally short circuit transistor
Q20 for example a too high tension lies at the resistance, the high
achievement makes for it from and it goes with defective. It is not
always foreseeable whether a transistor in the case of defect short
circuit or becomes high impedance, depends on the error situation, in
addition, on the internal structure, which gives way e.g. first: the
bond wires (becomes high impedance) or the silicon (can melt, with low
already, everything is made clean. Do you see like copper shine again
beautifully? The internal printed circuit boards are all down, there
are already worth it the baseplate to deseam itself. Put
on the water, soap
and the brush. Before however thoroughly superior where only little
water drauf is. E.G. do not ask the trafos and relays. Naturally as few
as possible into the potentiometers or the volume control, which leave
themselves front part (potentiometer and switch) and rear part
(preamplifier) well to take off here.
devices shine even again little. On the large plate is only rough wood
at construction units drauf, for which the water does not make
anything. Complete dividing and the large plate, would be so much work,
which hardly counts itself, cleans the whole ten thousand wires and
cables to solder on off and again - thanks no - goes here also times
for the defective Transitoren Q19 and Q20.
further defective construction units more found, the time to the
assembly tingles/swarms in the fingers.
There see, one both to the output stage with the spare tansistors
runs at both channels of the long PCB.
The photo shows the output voltage at 4 ohms a load. I have here times
untwisted on 36 V amplitude with a frequency of 2600 cycles per second.
Is small still little more amplitude, afterwards the amplifier begins
however with clipping. It
brings these 36 V at 4 ohms at the scope
with that orginal transitors. The radiator box will very warmly
not to recommend for continuous operation with such to a sinusoidal
RMS of Watt
thereby is meant the achievement in warmth, which would convert the
sine equivalent DC voltage in the resistance in warmth. In other words:
the sinus-wave voltage shown with the amplitude of 36 V would heat the
load resistance on a certain temperature. DC voltage of 36 Volt/1.414 =
24.445 V would heat the load resistance exactly on the same temperature
as the sinus-wave voltage.
A desire the
orginal loudspeaker cables connecting terminals had to be replaced with
socket carrier must be expenditure-soldered, the banana sockets can be
mounted simply not on it.
now a small pretty peace of wood
is to serve that then from the rear on the rear wall one screws. Thus
is written "chamfers" correctly.
About the measure with the wood
one can argue. Purely electrically (Ohm's resistance) it does not bring
to anything, perhaps that here: a gilded banana plug and a gilded
socket do not oxidize over years, the contact resistance remain
constant, as long as the spring action remains (nickel plated goes
naturally also). Some c-clamps loosen with the time a little, do not
control there occasionally did not operate. Favourably is the banana
plugs solution also, since a short-circuit actually only heavily in
addition-get is. If one considers the fact that with both amplifiers
the output stage transistors went broken then is the risk of short
circuit not at all on the light shoulder to take times in such a way.
How quickly does it happen that a few kupferadern are not under-wedged
correctly and pluses and minus to touch oneself? Particularly then if
one has it hasty, the light bad is etc.. Yes, that is an advantage of
the banana sockets, conclusion with the Gefummel, different
loudspeakers and amplifier jerk twitches exchangeably. It will look
nice certainly also.
A wood from solid nut tree heartwood
does good services. Shows the untreated condition.
combination looks board and sockets nicely. The wood was rubbed in to
the protection with a hard oil, as wood preservation and at the same
time little more color and gloss.
The transistors was ordered with www.ampslab.com.
The only source, which I found, which had at the same time the PNP and
NPN types at the camp. Large selection of obsoleter Transitoren leads.
In the meantime also the new condensers
arrived and wait for the installation. None are used "approve
of" in addition, no "expensive"
condensers. One can lead endless discussions across it which the best
is. The best never gives it, each solution intends and disadvantages.
The development of the loudspeaker
connections requires warmth and patience. Here a hot-air dryer with narrow air duct carried
good services out. During a connection easily copper up-waved, sorry.
The printed circuit board cleaned with white
spirits again inserted. Wires are typically held for mass production
briefly, in order to lower costs to remain electrically short as well
as over. When repairing occasionally nerved.
That was an idea the plate with the sockets
to connect - did not function. Thinner better flexible wires were used,
above with flexible isolated lines, so that sufficient distance to the
disturbing resistances can be kept. The connections of orginalen
plastics loudspeaker sockets, do not sit centrically like the drillings.
The printed circuit board in the inserted
condition. Here it happens closely. The danger the fact that bright
sockets and e.g. the wires of the resistances touch themselves
somewhere are given i.e. precisely inserts the plate and checks for
sufficient isolation respected and above all thereafter everywhere well.
Inserted the small Nussbaum
wood looks well and fits the black housing. The
socket-head cap screws can be tightened simply. The size fits exactly,
so that the plus and minus symbol remain still visible.
installation of the wood already requires something fate, patience and
time, but now is it in it. Perhaps the installation for you would be
also relating to crafts no problem, but someone that electrotechnically
little experienced is, can fast a support here shoot, a small
again-created surveyed short-circuit can the output stage damage. Check
thus either fingers really completely exactly away or afterwards.
Output stages (X07-1670)
Now it goes to the printed circuit board
side of the output stages. First a cleaning with white spirits and
brush. There still fluxing agent remainders and a factory-installed
protective layer, which is properly dirty with dust meanwhile.
The output stage of the other channel is
exactly dirty, to their
however was already times repaired, clearly to see at the not cleaned
soldered connections, fully with fluxing agent remainders. Electrically
with a low impedance output stage the not much constitutes, is however
the component side of the right output stage
is also still dirty dirty, the dust must away. Bent and bucklig
inserted of resistances.
Also this old Siff, the surplus thermal
compound verdreckte meanwhile must now down. Always the hands smeared
all the same where one touches. Wipe away with a rag strongly. The mica
disks are naturally also deseamed and checked at the opportunity for
damage. But caution the disks break easily, do not bend.
Like the white spirits cleaning and drying
with the hot-air foehn look the printed circuit board again correctly
cleanly. Even emitter resistances shine again like tooth white from the
advertisement. Thus it makes for fun on it to work. That is the left
output stage, which ran already apparently, it with A and C was marked
(assistance placing the transistors)
We begin with the exchanging of the
electrolytic capacitors. Here the expenditure-soldered C4 with
47µF/10V. Replaced by 47µF/25V. The
progress of the last decades becomes apparent also in the size, a
comparable from old days would be larger.
When the assembling of the output stage
transistors on the fact absolutely it respects that no
short-circuit between transistor package
(collector) and the radiator box develops. After each exchange of an
output stage transistor this must be absolutely examined with an ohm
meter or a continuity tester. An ohm meter can indicate however by
condensers joined in parallel varying values, e.g. a few hundred ohms,
that is normal. But on keinenfalls only few ohms - then amplifiers in
danger! Also guarantee that the probe tip to the anodized radiator box
has bright good contact, measuring instrument before examine.
Also the Elko c1, a 1µF/50V was
exchanged. With this capacity it offers on directly a more favourable
foil condenser to use (the yellow is the new 1µF/63V).
Oha, which is that that? Defective resistance R4 with 62 ohms in the
output stage right. That was noticeable to me in the verdreckten
condition, the surface was still whole already, only he was easily
brownish in a place, that is often an indication for too much warmth.
By cleaning and the pressing with the brush the truth came to the
light. It shows the carrier body was already as weak, which left easy
affecting with the brush in to break. An OK resistance does not make
that for nothing at all. The broken resistance had possibly
still something of its desired value, so that the circuit still
functioned, it would be however a clear Kandidant for a loss in the
next time "a usual construction unit that
because of washing now accelerated broken would go, soll's nevertheless
calmly equivalent broken to go, I remove
it, rather with me than in the next year with you in the living room".
Such a confirmation comes as called.
We throw nevertheless times a view of the
output stage left. The resistance R4 with 62 ohms, soldered there, is
resistor, that has another design. The replacement is a
standard 0.7 Watts metal film resistor. Aha, which is also the output
stage at that was already times repaired. Exactly this R4 was
already times broken. It is pure speculation why: R4 is in the event of
an error overloaded and thereby into death is also pulled. A view into
the circuit can clarify that.
How is the resistance replaced? In the ideal case with a larger 62 ohm
layer of metal/metallic oxide resistance, e.g. a 1-2 Watt resistance. I
have however at present unfortunately no larger layer of metal
available with 62 ohms. One can in addition, somewhat loadable 62 ohms
a themselves build oneself. For example from four pieces 0.7 Watts
standard layer of metal, interconnected as in the picture, sufficient
maximum energy dissipation has and is electrically and mechanically for
this application like that correct.
the arriving transistors
are tested at the
curve tracer whether they function and also got over transport.
with such older beautiful tube equipment a
Tektronix type 575, the characteristics of Transitoren can be
represented. Here a NPN transistor is attached. The transistors are
At both output stages the 62 ohms of R4 of
resistances are exchanged. At the output stage left even still clearly
a brown mark is to be seen, that has as a cause warmth under the R4 on
the plate. That is the printed circuit board with the small 62 ohm,
which already already with an earlier repair once one exchanged.
It became so slow excitingly in the output
stage left. A view into the connection diagram shows that R4 and D2 are
positioned in series, an investigation of D2 in the output stage left
shows these as defectively and in both directions high impedance, thus
broken. By the measuring instrument display (upper contour) one can
recognize "OPEN", that was an examination in flow direction, normally
should in the ok case approx.. 600 mVs its. The diode replaced with one
from the partial carrier.
Hier und heute wird
consideration the defect of the left output stage side became clearer.
Possible that a NPN output stage transistor went defectively through a
high river (why also always). The collector basis distance melts to a
short-circuit and thus is positioned to R4 suddenly in series with the
diode D2 at +66 V, high river flows by the PNP Q2 driver
2SA2633, the whole flows partially also away into the Q19 on the long
power Amp plate (X00-2010) (B)
and can the destructive work fortzsetzen there. Whether that was
everything also really like that, I cannot say with security.
In the output stage right, the Q2 driver transistor 2SA913 is broken.
Its basis emitter distance is high impedance. Probably also the right
output stage died over the same mechanism as the left output stage.
Always the same broken: either R4 or D2, here now even still the driver
Q2 and also the Q20 + 180 ohms of resistances on the long plate.
Transistor Q2 replaces by similar types.
The driver transistors were installed with
this amplifier everything without thermal compound on the radiator
box. Something thermal compound improves (according to
manufacturer) the heat transfer over up to 50%. The Treibertransitoren
was expenditure-soldered, examined and provided afterwards with
After that the output stages finished and
examined are them with plastics 70 protective varnish were injected.
Plastics 70 is for many years a protective varnish proven in
electronics, it is inexpensive and simple to use. The top sides one did
Both output stages in the painted condition.
The lacquer is through solderable, i.e. later solder repairs are no
problem. At the market there is many electronics lacquers for most
Power Amp (X00-2010) part
Now to the long printed circuit board power
Amp (X00-2010) (B) is behind the thick Elkos. The lacquer at the lower
surface is dirty. It was cleaned before with soapy water, enfernt
however only the rough and the dust. Here a solving cleaning agent
helps e.g. white spirits.
At power the Amplifier (X00-2010) (B) are
exchanged all electrolytic capacitors for new parts, there were also a
few surprises. In the lower half everything is which because
of this amplifier was already exchanged. The parts with the white
Kreuzchen are defective all. In this printed circuit
board two Elkos C19 and C20 for each 1µF/100V were
defective, it are the two small Elkos down right.
Here still another example like the electrolytic capacitors became smaller. They
did not become smaller only, but regards electrically also better. In
the example the dissipation factor of 0.065 to 0.018 and the spare
series resistance ESR improved reduced from 88 milli ohms on 25 mill
ohms (@120 cycles per second measured with HP
all electrolytic capacitors (except C19 and C20) in power the Amp (B)
correct. The orginalen condensers did not show noticeable
loss of capacity, dissipation factor and ESR after all the years in
order. Leakage currents hardly measurably. Nevertheless was worthwhile
itself exchanging for new condensers, which are new series in their
electrical values improved. The temperature range amounts to with the
new series 105°C with the old 85°C. The new ones have
about 1000 hours specified life span with 105°C and may
thereafter a loss of capacity of the order of magnitude about -30% show
(one considers, the manufacturers spezifieren the life span often
differently). Only 1000 hours with 105°C? - that is not so few,
because aging obeys an exponential function vs. temperature, i.e. with
25°C lies the life span then perhaps at estimated approx.
completely roughly 40,000 hours.
life span of an electrolytic capacitor depends mainly:
the quality of the condenser
the local ambient temperature in the amplifier.
Ripplestroeme the condenser must carry (a question circuit Design,
construction unit dimensioning and the application), the more highly
the alternating current by a condenser, the more internal warmth
ensteht in it and co-heats it, the increased temperature again favours
constantly continuing procedure of the loss at electrolyte, thus the
capacity sinks. A Low ESR Elko like here the again blocked has a lower
internal Ohm's resistance, after p=i*i*ESR ensteht in it less internal
warmth. Straight one for applications in circuits, with which it must
carry high alternating currents is a Low ESR ideally. For many
applications with low alternating current a Low ESR is not necessary
and a standard type in harmless environment can thereby
become very old. All types whether standard, Low ESR, 85°C,
105°C, or 125°C have all their respective pro and cons.
the condensers was meaningfully, particularly in the case C19 and C20,
which were totally defective. Why are these broken gone?, I do not know
Power Amp (X00-2010) part
Now it goes to the large printed circuit
board with the thick electr. caps.
It is the power Amp (X00-2010) A. Er looked relatively good.
The large printed circuit board from the housing to remove I saved,
that am much wire soldering
and mounting, dividing am
not as comfortable here as the past. The cleaning on the lower surface
with white spirits can be settled also in the inserted condition,
exactly the same happened it also with the exchanging of the condensers.
let constantly show, what was carried out for still improved
dissipation factor and ESR in the area of the electrolytics
by all manufacturers around the size to reduce, in this case even with
higher tension strain (needs more voltage
strain more volumes, compared with the same) in addition vs. frequency.
Also the power Amp (B) printed circuit board
was over-painted to the conclusion with plastics 70.
Now are times again an assembly and a first
intermediate test of emergencies. Everything compound and switched on -
see there the amp runs now
on both channels, but comes not yet correctly tested, later.
The phono amplifier is in the rear part quite
protected between two sheet metals hidden. The printed circuit board
carries also the Aux, Tape, tuner of entrances, moving
coil and moving magnet inputs.
The whole plate consists of many single transistors and
discrete construction units.
A cleaning of the phon amplifier is also
New condensers for the phono
player amplifier contains bipolar coupling
electrolytics in the signal path, this by foil condensers
Electrolytic capacitors at the phono
amplifier exchanged. The upper left left corner is the
Moving Coil sector, the most sensitive signals in the amplifier.
thick foil condenser package with second
adhesive together adhesive.
the exchanged caps
from the phono amplifier.
the back is cleaned with white spirits.
finished printed circuit board with
plastics 70 paints
Everywhere cable and lines where one looks,
all potentials from small to high.
the equipment does not have a protective
grounding connection, the mains voltage runs by the equipment from the
rear forward. If one of these wires were abkracht and the housing
affect should, voltage is
because of the housing, well to control.
tone control and first
amplifiers stage (X1-1520-10) (X11-1520-813)
To the front. Aluminum front plate down,
(amazingly simply went) the front cover to hinge away. On the right of
the change over switches, on the left of the actual preamplifier for
all signals, the bass & treble
controller, subsonic switch
without wanting to step now possibly someone
too close one, the way like that here constructionally fastened already
is a little a Gefummel. Fortunately that must be opened here only rarely..
the two printed circuit boards and the
housing are connected by short wires. The rear printed circuit board
has some cable links. Good contrast: on the right of the noble
potentiometer, left many wires.
Printed circuit board with the bass and
altitude controls. To see the small yellow foil condensers are instead
of the Elkos. The two thick bipolar 47µF Elkos were
not replaced, they remain in it, them are still ok 47µF by
foil to replace is now nevertheless somewhat too violent to me in the
manufactures printed circuit board with DC
ON OFF switch, Subsonic and High filter. One considers also down right
within the range of the transistors the brown discoloration of the
printed circuit board by warmth.
like cleaning and painting also the back of
the DC ON OFF printed circuit board looks again correctly new.
the back the clay/tone control printed circuit board with the bass and
heights automatic controllers after cleaning and painting.
exchanged Elkos, them was electrically
still all in very good condition. The small black left are the bipolar
Resistances heated the printed circuit
board. A heat nest in the left upper corner. Behind the next heater, transistors and resistances
of the other plate.
V of power switches and supplying and signal lines.
all construction units were so far exchanged, and the joy stood before
the amplifier to test. Said done - which went? Nothing. In such moments
annoyance does not grow nevertheless enormously, hours of the life
spent in full hope and it goes. Thereupon tested which it could be,
then finally found. The DC ON OFF switch has a bad bad contact also
still equivalent on both channels, completely indefinable. Thereupon
the switch exchanged for the functioning from the partial carrier. The soldering out requires something
patience, is however simple.
the picture center DC on off switch with the mechanical defect is
exact. With the first test that was not noticeable, can also be that up
and screw the previous together the effect favoured. On the right of
the spare part. The amplifier again screwed together, functions. After
equal the exchange of nearly 100 condensers one has already something a
mulmiges feeling whether everything goes. It is always the question in
the head, I all also correctly polarized inserted, is somewhere one of
the wires broken etc..
the contacts were well sprayed first with
contact 60, cleaned afterwards with the spraying laundry wl by the
replaced oxide coatings. With using contact spray try this
there to only spray where contacts are real, so that too much
surrounding dirt and oxide coatings are not along-solved, only again be
removed must if it at the contacts arrived.
the connecting cables of the printed circuit
boards were extended something that simple measuring at the printed
circuit boards became possible.
Again everything assembled
repair work in all peace without any hecticness or time pressure were
settled. I have sufficient time to taken also try the substantial
elements this amplifier types to understand. The work was limited to
substantial and simply feasible. One could have done still some more by
the reliability to increase, as well as still the sound quality to
increase, would mean however enormously much additional expenditure.
Nevertheless up to now about 50 to 60 hours at work resulted. The work
can be justified only with the background of the enthusiasm and the
profit at experience, from economic view may one to such work only not
at all struggle marriages, better only not at all to thinks - stand in
no relation to the equivalent of the amplifier.
report is to tune also a little the people thoughtfully, which the
opinion are: "want favorably times fast defective equipment to buy or
too ersteigern" and then try it in one afternoon repaired to get.
Sometimes as loosely easy as many it does not go introducing themselves
and workshops to assign can become expensive, since also must invest
this much time, although they already possibly bring along experience
with this types. Workshops stand with the high hourly rates in Germany,
which must require them to repair under high pressure the equipment
with small expenditure of time. For cosmetic operations like all Elkos
is there no time exchanges, although the repairing would spend surely
very gladly more time with the equipment.
that that to settle can do all this.
addition, the report is to motivate owners to seize at least times
about it to think with the next defect similar measures. Electronic knowledge
is actually necessary actually only for the repair, the remaining work
is only questions of the fate relating to crafts.
the conclusion still another few serious-meant references to owners:
please never the output stage at the exit
closes briefly, also not for a short moment
on when attaching the loudspeakers cables
it well, solder before easily the ends
none for thick cables, which do not fit into the sockets
the clamps at the equipment and at the loudspeaker well, control
regularly the firmness of all connections at amplifiers and
wires may not touch themselves, also no contact to the housing
the cable laid in the room carefully
the connection of the loudspeakers (particularly stranger, which did
not run ever at the amplifier) should be always based with an ohm meter
between pluses and minus on the cable not attached yet. The accuracy of
the ohm meter is here hardly of importance. The read off measured value
should lie in the order of magnitude of the nominal value of
loudspeaker impedance, e.g.. 4 or 8 ohms of no case
loudspeaker attach, with which ohm meter indicates only very small
fun when hearing.