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G9000 pop in left channel

All caps correct value and voltage, polarity correct on the driver board?

Could be one of transistors back in the driver stage, unusual for this amp but could happen....

If you have a scope, you can just follow the popping back into the driver stage and hopefully identify the culprit.....

I think it will be a transistor....
 
Driver may be it. There are a couple fuse resistors on the driver boards also that should be replaced. At this point i'd replace all the transistors, fuse resistors, and recap it.
 
I've completed the recap of the G9000, including the 2806 board. I rechecked the caps on the "bad" 2806. The are all good. I checked the R17,R20. They are both right at 150 Ohms. One think I have noticed on this 2806 is that I can adjust offset down to -.15mv or so but then it will swing over to +.4 volts and then swing back to the -.15mv or so. This takes place every 20-30 seconds or so.

Does anyone have part numbers for the 2806 transistors? Thanks!
 
I have adjusted the offset down to .3mv, but it will then swing way up to .4v or so. This also corresponds with the small or soft pop/click sound that I hear via headphones or speakers. As mentioned earlier this is with the amp coupled or de-coupled. The pop or click was present before the recap.

As always thanks for helping out!
 
Jot down the current part numbers and their specs. This will make it easier for us to help you.

You have the drivers coming already. That may fix it. The bias trimmers need to be replaced also.

Quit playing it as the bias may not be tracking right.
 
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I have checked the resistors on the F-2806 and they are fine. I guess that I'll move on to the transistors. I pulled them and checked with a meter, they checked fine, but I don't think that really gets you anything.

The transistors parts are:
TR05,08 2SA-818 0, Y -as listed in the manual
TR06,07 2SC-1628 0, Y - as listed in the manual

Don't know if I would need to replace TR 09 or 10, but here are the part numbers:
TR09 2SC2238 0, Y
TT10 2SA968LB 0, Y

I also have a 901DB that I cross referenced. The TR05,08 and TR06,07 have what look like newer transistors. The part number taken from the transistor are:

A939 B KS - TR05,08
C271 B KS - TR06,07

Any help in replacements would be appreciated.

Thanks!
 
C271 B KS = MJE 340
A939 B KS = MJE 350

TR09 2SC2238 0, Y= MJE 15032
TT10 2SA968LB 0, Y= MJE 15033

You can get the G variant also which is the "lead free" version.
I have used these many times as subs and find they work very well.......
 
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ManyMoonsAudio said:
LOL! Kevin..... Hard to keep you off a turd huh...

I dissagree with your rec. for these:

C271 B KS = MJE 340
A939 B KS = MJE 350

They will work, but I don't think they even list a gain spec for these.....??
Click to expand...

LOL........

Someone else mentioned there was no gain spec for the 340/350 too......they do work, and damned if I can hear any difference, but as you have a line on a better sub....why not....

I just jammed a 340 in the hfe meter, came up at 100, and the 2071 I put in there came up 120, so yes they are a little lower on gain on average......

I always test the hfe, because the thing with these MJE's is it seems to vary a lot, some are low, down at 70ish, but then they can be up around 100, sometimes even more.....
So I always by shitloads of them and test them before I use 'em.......
 
Thanks guys for all the replacement parts recommendations. Don't know how far to go to rebuild the 2806, which when done will hopefully get rid of the recurring spike in the offset voltage.

There are a couple of other transistors, TR10 and TR09. These are the bigger guys on the board.

TR09 2SC2238O Y
TR10 2SA968LBO Y

I'll replace the resistors also. Is it necessary to replace all or only certain resistors? Metal Film?

Also there are a couple of Diodes, Don't know if they should be replaced or not?
ZD01
ZD02 EQB01-22.
 
redcbx78 said:
Thanks guys for all the replacement parts recommendations. Don't know how far to go to rebuild the 2806, which when done will hopefully get rid of the recurring spike in the offset voltage.

There are a couple of other transistors, TR10 and TR09. These are the bigger guys on the board.

TR09 2SC2238O Y
TR10 2SA968LBO Y

I'll replace the resistors also. Is it necessary to replace all or only certain resistors? Metal Film?

Also there are a couple of Diodes, Don't know if they should be replaced or not?
ZD01
ZD02 EQB01-22.
Click to expand...

These amplifiers are actually very reliable, and in my experience I have only found that R17 and R20 which are the 1/4watt 150watt resistors are the ones which give trouble....
However, on mine I replaced (for the sake of preventative maintenance) these ones too. You dont need to worry about the other ones....
R23 47Ω 1/2watt
R24 47Ω 1/2watt
R25 390Ω 1/4watt
R26 390Ω 1/4watt
R29 4.7Ω 1/4watt
R30 4.7Ω 1/4watt
R31 10Ω 1/2 watt
R32 10Ω 1/2watt
I used all 1% metal film.

I wouldnt worry about the diodes.....

TR09 and 10 are the drivers, and you can use MJE15032 (NPN) and MJE15033 (PNP) in this place. These were the ones Paul was suggesting could be popping....
 
Thanks guys for all your help. I'll get the parts ordered up. I'll order x2 and do both boards. Got my fingers crossed that it fixed the bad board.
 
The problem is probably the differential pair, the first two transistors in the power amp driver board. It's unusual for it to be a soft pop, but hey, it's a G9000. Before you change everything, I would try changing out those two, just to see if it's them.

Hey Kev!
 
Trnsfmr said:
The problem is probably the differential pair, the first two transistors in the power amp driver board. It's unusual for it to be a soft pop, but hey, it's a G9000. Before you change everything, I would try changing out those two, just to see if it's them.

Hey Kev!
Click to expand...

Hey Jim, this amplifier has a dual FET rather than a Diff pair, very rugged component........never seen one fail......
 
Right Kev, but if it walks like duck, quacks like a duck, you know. . . . Maybe it's a duck. Maybe the characteristic of an FET differential pair going bad would be a soft popping. He says it's intermittent.

It's so easy to do, and you don't have to do any troubleshooting. And of course, anything can go bad. What's to lose?

:D
 
Trnsfmr said:
Right Kev, but if it walks like duck, quacks like a duck, you know. . . . Maybe it's a duck. Maybe the characteristic of an FET differential pair going bad would be a soft popping. He says it's intermittent.

It's so easy to do, and you don't have to do any troubleshooting. And of course, anything can go bad. What's to lose?

:D
Click to expand...

True Jim, however we are working within the confines of what we know could be the problem with these particular amplifiers, it may well involve the diff FET....
It is the obvious diagnoses for this particular symptom, and in a Sansui with Diff Pair transistors, I would agree.....
However these amps are different, and those FETs are damn near indestructible which is why at this point it is not a consideration........

Could swap the FET from the other channel if you wanted, that way you could eliminate it.....
I checked my usual sources for these FET's and no one has them in stock....could be difficult to find if it does prove to be the problem.......
 
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Because of their known unreliability elsewhere, my money is on:-

TR05,08 2SA-818 0, Y -as listed in the manual (replace with 2SA1837 - Mouser)
TR06,07 2SC-1628 0, Y - as listed in the manual (replace with 2SC4793 - Mouser)

Unless I am mistaken these are the famed 'uniwatt' transistors - not good.

Carry on...
 
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Hyperion said:
Because of their known unreliability elsewhere, my money is on:-

TR05,08 2SA-818 0, Y -as listed in the manual (replace with 2SA1837 - Mouser)
TR06,07 2SC-1628 0, Y - as listed in the manual (replace with 2SC4793 - Mouser)

Unless I am mistaken these are the famed 'uniwatt' transistors - not good.

Carry on...
Click to expand...

:thmbsp:
 
Thanks guys for all the info. Parts should be in no later than Friday.

Got a question about the TR05 through 08. I see a few different replacement part numbers.

TR05, 08(2SA-818 0, Y) Replace with 2SA1837 or NTE292
TR06, 07(2SC-1628 0, Y) Replace with 2SC4793 or NTE190

Also on the 901DB with the same driver board
TR05, 08(A939 B KS) Replace with MJE 350
TR06, 07(C271 B KS) Replace with MJE 340

Until I get the parts in I guess that I could remove parts from a known good board and put them in the bad board.

With the different part numbers between the 901DB and the 9000 for TR05 through 08, I'm a little concerned about possibly using the parts from the driver board on the 901DB to test the components on the 9000 driver board.

I would assume that the TR05 - TR06 transistors from the 901 driver board would work fine in the 9000 driver board, even though they are different part numbers?

Thanks again.
 
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