kustom k200b repair

[maxk]

Hello, first post here, apologies if I am missing something or in the wrong spot.

I am working on a k200b poweramp that had a blown output section. Most of the transistors were bad, replaced q1-4 q703-9 and the majority of associated parts. The diode cr702 was blown. I didn't have a suitable chassis mount diode so I replaced the bias string with a transistor vbe multiplier, which seems to be working fine.  The amp now works and passes audio, but I can't get the output transistor voltages on each side to match.  When the collectors of q3 and q4 is -.1v the emitter of q1 and q2 is .125v.  All of the resistors are 5% or better, 1% where indicated on the schematic.

I'm not too experienced with ss power amps, so please let me know if i'm screwing up the nomenclature or leaving out obvious info.  Any help is greatly appreciated. Thanks!
schematic

[g1]

How much each output device conducts is related to the bias circuit.
As you have made modifications, the stock schematic does not show the whole picture.
Post a schematic that includes all your circuit changes.

[maxk]

Sorry, didn't see the now obvious "click or drag files here" button.

Here's an updated schematic and voltages. I just copied the vbe multiplier from another site, probably not wise to copy paste parts of a bias circuit that I don't fully understand, but seemed like a good idea at the time. The bias trim pot seems to keep the ratio about the same, so I can make either side match fairly close to the schematic voltages, just not at the same time. Both pairs of output transistors measure the same, so I don't think it's just a mismatch.  I have already tried a few different transistor substitutions that didn't seem to change much. 

[g1]

With no load connected, is there any DC at the output?  What is the DC voltage drop across each of R737, R738 ?

[maxk]

.01v dc on the output

r737 - .0873v
r726 - .0885v
r727 - .0889v
r738 - .0882v

[g1]

Those resistors are shown as 1 ohm on the schematic.  If so, you have idle currents of around 88mA per output device.  That seems kind of hot, 10 to 20mA would be a better target.  Adjust bias to get around .01 to .02V across each of those resistors.
Then again check for DC at the output.  If it stays around the 10mV you have now, that is good.

[maxk]

Thanks for the advice! Set the bias cooler, dc on the output is now below what my meter can read.

[J M Fahey]

It is safer this way.

I mean, *there are* Class A SS amps, with strong idle current all the time, some Audiophiles swear by them, but then they have HUGE heatsinks and are designed to run very hot all the time.
Not our regular Guitar/Bass amps.

Not kidding: all those transistors and massive heatsinks for a puny (for us) 30+30 W RMS amplifier:

[maxk]

Yes, not much of a heatsync on that kustom.  I was being dumb trying to match the numbers on the schematic instead of doing the math myself.  Should have known better, but making transistor subs is still pretty intimidating for me. Won't make that mistake in the future.  Thanks again!