Crown microtech problem

[g1]

Here are a couple papers on 'grounded bridge' or 'flying rails' type circuits:
https://music-electronics-forum.com/...tch?id=1000389
https://music-electronics-forum.com/...etch?id=853796

[Bigdrums]

I read both the tech papers and noticed something that could make it difficult to troubleshoot. From the Fender paper:

Note: This is the reason that the speaker (or an appropriate load) must be connected when servicing these amps.

The schematics of "grounded-emitter/flying rail" amps refer to "C.T." This stands for "Center Tap". This is the same point as the positive terminal of the speaker.

Usually with an amp that is not yet stable enough to supply full mains voltage, I would not have a load connected and no signal applied. Meaning I would want to make the amp work properly without a load connected first. I understand that they are saying you need the load to complete the circuit for troubleshooting, just not with the power on. Is that correct?

[Helmholtz]

I think that "grounded bridge" and "flying rails" (aka "grounded emitter") are quite different principles.
Particularly, the "grounded bridge" amp uses a unipolar supply and 2 out-of-phase (half-bridge) power stages,
while the "flying rails" amp needs a bipolar supply with a CT and uses a single powerstage.
Both topologies have in common that the rails are flying wrt. ground.

[Bigdrums]

Looks like I need to find a couple of 6492 main output transistors. No luck yet though

[g1]

I think that "grounded bridge" and "flying rails" (aka "grounded emitter") are quite different principles.

Ok. I think I misunderstood your earlier statement here: https://music-electronics-forum.com/...91#post1000391

[x-pro]

Don't break your amplifier. Entrust its repair to professionals. To repair it correctly, you should always keep in mind the non-standard connection of its output stage. And if you switch the amplifier to bridge mode (make the whole amplifier single-channel), you will have a headache from understanding its operation.

[x-pro]

Here are a couple papers on 'grounded bridge' or 'flying rails' type circuits:
https://music-electronics-forum.com/...tch?id=1000389

In the article at the first link on page 3 (Figure 8. Class 'H' Supply) there is a slight error in the figure where there is equality between the supplies. It is strange for a method book to make such errors.

[Helmholtz]

In the article at the first link on page 3 (Figure 8. Class 'H' Supply) there is a slight error in the figure where there is equality between the supplies.

Actually severe errors in figure 8.