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Pioneer A-27 Power Supply Issue

Nothing to be sorry about! I can usually figure out what you mean by context. Then adding in the specialized Electronics terms make it even more difficult for you. I have helped people all over the world fix their equipment, I have a thread going with a man in Slovakia, as well as another one in Germany. That is part of the fun, for me anyway :beerchug:.
 
Those numbers look good to me.
With the power supply board installed does the amp pass the DBT test with 120W bulbs?
 
I am glad that you picked up my thread, thanks for the patience! If this is a source of fun - all the better!
This evening (only about an hour away) I'll lift a glass of beer, as you depicted, on your success in helping me (and your health of course :beerchug: :thumbsup:).
If you are actually in eastern colorado, you're 8hrs behind Germany, and your sunday barely started...

I installed the power supply back in, and it passes both 60W and 120W test.
I notice with 60W, it stabilizes with a moderate glow after some seconds, with 120W it is very dim (after some seconds).
I guess this is OK, since current is split on both bulbs then - instead of completely going through one only.

Now freshly measured on pins of power supply (power amp still disconnected), with 120W DBT, in brackets the nominal value:
pins 1 and 2 (-33V) -> -31.6V
pins 4 and 5 (+32V -> +31.0V (with current VR1 setting)
pin 6 (-66V) -> -64.2V
pin 8 (+65V) -> +63V (with current VR2 setting)
pin 10 (+0.7V) -> +0.72V
pin 11 (+1.6V) -> +1.5V
pins 13 and 14 (+24V) -> +23.4V
pin 16 (+0.7V) -> +0.72V

The values change a bit over time, in second or third significant digit, but I guess that is also OK since unit is each time only a couple of seconds after being switched on. I averaged over some seconds.

Checking these numbers, agreed that I take same measures without DBT now?

Best regards,
Frank

OT: You used some german words, are you connected somehow to germany?
 
Yes, I am in Eastern Colorado,Time Zone -7. 8 hours between us, it must be evening where you are.
Those numbers look good. You can go off the DBT for now.
Let's take a strategic path towards getting this going.
The next thing to do is make sure the Surge Killer relay is working, what is the DCV on pin 12? Should be about +51vdc. Can you hear or see the Surge Killer relay (RL1) pull in at power up? It will be pulling in very quickly after power on when not using the DBT. If so lets check some other power supply voltages.
Measure unregulated DCV on main power supply capacitors:
C7, should be about +61vdc:
C9, should be about -61vdc:
C8, should be about +61vdc:
C10, should be about -61vdc:
 
Ok, new/next values of power supply, now without DBT.
I used VR1 to adjust on pin 8 and VR2 on pin4/5.

pin 12 (+51V) -> +51.9V

pins 1 and 2 (-33V) -> -32.5V
pins 4 and 5 (+32V -> +32.0V (adjusted by setting VR1 accordingly)
pin 6 (-66V) -> -66.3V
pin 8 (+65V) -> +65V (adjusted by setting VR2 accordingly)
pin 10 (+0.7V) -> +0.72V or +30V to +34V -> here is an intermittency problem, see text below
pin 11 (+1.6V) -> +1.5V or about +24V, same intermittent occurence as on pin 10, see text below
pins 13 and 14 (+24V) -> +23.7V
pin 16 (+0.7V) -> +0.72V or about 30V -> see text below

Further measures on main power supply capacitors (these are no originals anymore and been replaced by 27000µF / 80V)
C7, should be about +61vdc: -> +61.5V
C9, should be about -61vdc: -> -61.6V
C8, should be about +61vdc: -> +61.5V
C10, should be about -61vdc: -> -61.5V
-> Seem to be good.

Intermittency problem:
Switching on with120W DBT, in many cases, pins 10, 11 and 16 show as expected. It can be observed, that in this case several relays click:
The first immediately after switching on, then two more after about 1 to 2 seconds, and then about two more later, it all takes about 5 seconds.
That is quite the sequence I remember as it was formerly (case A, regular, as expectable).

But in some cases, there is only an initial relay click (and maybe the second, hard to determine), and then no more.
In this case, pin 10, 11 and 16 voltages stay high (case B, irregular).

Switching on without DBT, mostly case B occurs (only initial click, maybe also one more, much softer click), but then nothing more.

I observed this and took voltages with at least 10 times switching off and on (after couple of seconds), with 120W DBT, and also without - more case A than B on DBT, mostly case B without DBT.

I hope my description is correct, and understandable.

Best regards,
Frank
 
Looks to me like the power supplies are all good now.
The Protection circuit, muting and relay switching are all logically mixed together, gotta study the SM. Those functions are unreliable on the DBT, you have to be off the DBT to verify the timing and proper function.
Also working on getting a better schematic.
 
http://www.wwdsltd.com/files/PioneerA-27Schematic.jpg
Here is a link to download a full schematic in one drawing. It is much easier to follow than the one in the SM. Be aware that it is for the KU (USA, 120v) version, so the primary side of the transformer does not have the multi-voltage option in the drawing that the S or SG version usually sold over there has. The main part is usually the same.
The source for this is a fellow AK member, Watthour.
 
merlynski said:
Looks to me like the power supplies are all good now.
Click to expand...

That is a good position to go on from.
I have the Kallhovde manual, with some EU-Model extensions, but the complete schematic in one picture comes in handy and is new to me. Thank you and Watthour (I knew him from his postings) for excavating this schematic!
I will go on as soon as possible, but working week has started and time is much more scarce than on weekends...

Best regards,
Frank
 
So, following the wire path from power supply pin 14 (+24V), I see it supplies to relay RL1 on Pin Jack Assy (pin 5 on GWX-212) coming pack to pin 11 power supply.
(It also supplies a relay on Headphone Assy (pin 51 on GWX-210), which comes back to pin 10 on power supply.)

As I measure +24V instead of 1.6V on pin 11 power supply, when the relay does not click, this seems to be simply the output of pin 14 then.

Is it correct to assume, that either the relay is bad or more likely Q21 of power supply does not allow the relay's current to flow?

Edit: Added pin-#
 
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The +24vdc on pin 11 indicates that the relay coil is good, but Q21 is not conducting current to pull in the relay.
Measure dcv on pin 16 (the base of Q21), sb about +0.7vdc.
Measure DCV on the collector of Q17, sb about +16.2vdc.
 
Here the values:

Power Supply, with DBT 120W, dcv pin 16 -> +0.72V
Power Supply, with DBT 120W, dcv collector Q17 -> +19.2V

Power Supply, no DBT, dcv pin 16 -> 0.00V
Power Supply, no DBT, dcv collector Q17 -> 0.00V

Tape Mon: -> SOURCE
Function: -> TUNER

The Function setting could be different than at previous measurements, as it could have been AUX before; I checked if all lamps were still going.
 
The results on the DBT appear to be within tolerance. The results without the DBT (presumably on 240V line power) are confusing.
 
I wonder why, with DBT@120W, values are OK (except collector Q17 is a bit high), but without DBT it is not.
As I mentioned, in some cases ('case B'), also on DBT@120W values are bad.

Line Power is 230V, measured before.
 
Q17 is high. It would be good to know the emitter and base voltage measurements.

If D19 is damaged, the result could be a higher base voltage.
 
I took measurements, all on Power Supply, with DBT@120W and without DBT, each time after no more relay clicks come.
(Power Amp PCB is still completely disconnected):

Relay clicking sequence sounds familiar and is seemingly OK, takes about 7 to 8 seconds to complete:
DBT@120W, Collector Q17 (+16.2V) -> +19.3V ?
DBT@120W, Base Q17 (Kathode D19) (0V) -> 0V
DBT@120W, Emitter Q17 (0V) -> 0V
DBT@120W, Anode D19 (-2V) -> -1.48V ?

DBT@120W, pin 10 (+0.7V) -> +0.76V
DBT@120W, pin 11(+1.6V) -> +1.55V
DBT@120W, pin 16 (+0.7V) -> +0.71V
DBT@120W, pin 14 (+24V) -> +23.2V
DBT@120W, pin 12 (+51V) -> +39.8V
DBT@120W, pin 2 (-33V) -> -32.5V
DBT@120W, pin 4 (+32V) -> +32.0V

The same without DBT:
Relay clicking-sequence is missing. Only initial click appears instantly on switching on, then nothing more:
no DBT, Collector Q17 (+16.2V) -> 0.71V
no DBT, Base Q17 (Kathode D19) (0V) -> 0V
no DBT, Emitter Q17 (0V) -> 0V
no DBT@120W, Anode D19 (-2V) -> -3.2V ?

no DBT, pin 10 (+0.7V) -> +51.6V
no DBT, pin 11(+1.6V) -> +23.5V
no DBT, pin 16 (+0.7V) -> +0.00V
no DBT, pin 14 (+24V) -> +23.4V
no DBT, pin 12 (+51V) -> +51.6V
no DBT, pin 2 (-33V) -> -32.5V
no DBT, pin 4 (+32V) -> +32.0V

If I were on my own, I would now desolder, check and replace D19, (D17, D18), Q18, Q19 and Q21.
But that is only my laymans' guess.

Best regards,
Frank
 
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Simply for the sake of argument, can you report the measurement of the voltages across C7 and C8. Please take both DC and AC voltage measurements.


You could do the same with the main filter capacitors (18,000µF). .
 
Here are the values of the due measurements:

Power Supply, Pin 22 used as ground:
DBT@120W C7 -> +36.9 VDC
DBT@120W C7 -> 0.0 VAC
DBT@120W C8 -> -36.7 VDC
DBT@120W C8 -> 0.0 VAC

no DBT C7 -> +46.7 VDC
no DBT C7 -> 0.0 VAC
no DBT C8 -> -46.8 VDC
no DBT C8 -> 0.0 VAC

Main capacitors (not originals anymore, replaced by 27000µF / 80V), Chassis is ground:
(I am not sure if following cap designation sequence is mapping the manual: C7 is closest to unit front, then C9, C8 and C10 closest to back side?)
C7 -> +61.6 VDC
C7 -> 0.0 VAC
C9 -> -61.6 VDC
C9 -> 0.0 VAC
C8 -> +61.4 VDC
C8 -> 0.0 VAC
C10 -> -61.5 VDC
C10 -> 0.0 VAC

No value looks suspicious to me. Need more voltages?

Since the A-27 was working last two years as expected, before getting too warm recently (due to damaged D21 and D15), could the missing (disconnected) Power Amp cause this behaviour (due to not drop some voltages or alike)?

Best regards,
Frank
 
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That resolves the question anyone may have had about those rectifier failures. Those voltage measurements seem to be appropriate.
 
If no one has objections, then I will go on and check (and, in case, replace) D17, D18, D19, Q18, Q19 and Q21 of power supply.

Does this sound agreeable:
D17, D18, D19: 1S2473 (35V 110mA) -> 1N4148 (75V 200mA 0.5W)
Q18: 2SC945A (50V 150mA 250mW) -> KSD1616AG (60V 1A 750mW)
Q19: 2SD712 (100V 4A 30W) -> KSC2334 (100V 7A 40W) (or, at this position, sufficient if KSC2073 (150V 1,5A 25W)?)
Q21: 2SC1903 (150V 50mA 1W) -> KSC3503E (300V 100mA 7W) (or sufficient if KSC2310Y (150V 50mA 0.8W)?)


Best regards,
Frank
 
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