Traynor ycv40 low output

[nosaj]

i have a traynor ycv40 pcb version 9 with 1k sine into input I cannot get much more than 3 volts into a 8 ohm dummy load. i have replaced the power supply caps all of them. Also found 6.3 volts on tranny was actually 4 volts, so I subbed a 6.3 vac source in.
Any help or suggestion invited. Tomorrow i will scope the inputs of v1,2,3,4,5

v1 voltages pin1 150vdc pin6 139 vdc heaters 6.3 vdc
v2 pin1 153 vdc pin6 155vdc heaters here are 5.7 vdc
v3 pin1 45 vdc pin6 135 vdc heaters here are 6.3 vac

v4 pin3 390 vdc pin4 385 vdc pin5 -38
v5 pin3 388 vcd pin4 384 vdc pin5 -40

PT
wc7 wc8 24 VAC
wc9 300 VAC

OT
wc11 410

Let me know what if anything else I need to provide. Correct schematic for this amp provided by traynor

schematic-M581-1V8.pdf

Thanks,
Jason

[Jazz P Bass]

When faced with a low output I always look at the power tube grid Vac signal level.

If it's low, then the problem is before that section.

If it is not low: output tubes & OT is all that there is.

[supawah]

just throwing this out there...... on a lot of those combos the signal path goes across the ic'sthat drive the effects loop and the one that drive the reverb, so if that ic dies the signal path goes with it. I've had to replace that tl072 in a couple of those amps. just a thought

[g1]

V3 pin1 voltage is not right. Should be very similar to pin 6 voltage. Check R43 or bad solder somewhere to pin1.

[Jazz P Bass]

Ahh, the Fender 'let's eat the PI plate resistor' trick.

[g1]

Was that 4VAC heater voltage with the leads disconnected?

[nosaj]

Was that 4VAC heater voltage with the leads disconnected?

That was checking voltage at the tube pins 2 an 7 I think. But it also measured 4 volts disconnected. Power in is 120 volts on a variac.

Jason

[g1]

Was R43 bad?

[nosaj]

Was R43 bad?

Yes it was open, replaced it with a half watt 82 k previous one looked like a 1/4 watt(used what i had). Will have time to test tomorrow and update. i tell ya kids will wear you out.

Thanks,
Jason

[nosaj]

update. Hooked it up great volume and squeel swapped OT leads. Volume is as should be now.

Thanks a whole lot guys. I really appreciate it.

So now back to address the heaters . If I wanted to permanently mount a 6.3 volt transformer in there somewhere, only 3 tubes run off it 2 outputs an PI. It would need to be 2.1 amps or higher correct?

Thanks,
Jason

[g1]

You are correct. In this amp the DC the other preamp tubes run their heaters off is taken from a different PT winding.

[nosaj]

So is 2.1amps good or should I raise the bar to 3? Or do tubes only pull the mA specified in data sheet?

Thanks,
Jason

[g1]

The heater current remains constant, close to what the data sheet says, but you should probably leave some leeway. Your choices are probably for either 2 or 3 amps, maybe there is a 2.5A available. I would say to go with 2.5 or 3. This also leave option for adding an extra preamp tube or some other power tubes that need more heater current.

[52 Bill]

Okay I'll ask the obvious question here. Now that the other problems are fixed does the amp still need the new filament supply to work?

[nosaj]

Okay I'll ask the obvious question here. Now that the other problems are fixed does the amp still need the new filament supply to work?

Yes. still only getting 4 volts at the output heaters. voltage is the same 4 at the transformer connection also.

Jason