ANOTHER dead valvestate !

[Valvehead]

ok , i measured the transistors.

these will be E / B /C and in dcv

tr4 +3 / -8 / -8.7

tr5 -8 / 0mv / +0.6

tr6 +8.6 / +1.3 / +1

tr7 +3.4 / +8.5 / +8.5

tr11 +4.5 / +4.3 / 0mv

tr12 +4.4 / +4.4 / +4

dont know which is base etc.. on the last 3 , so measuring the legs left to right :

tr8 +3.4 / +8.6 / +4.7

tr9 +3.1 / +3.4 / +3

tr10 +3 / -8.5 / +4.2

[Jazz P Bass]

I cannot fathom what is pulling down those voltages so much.
For one, the voltages on the base of the output transistors is way high.
That would lead to the drivers being bad.

[g1]

What is the wattage of the bulb in your limiter lamp?

[Jazz P Bass]

A different post had arrived at a 100 watt lamp.

Even so, the last go round without the limiter, the mains fuse blew immediately.

Whatever is wrong, it sure is not obvious across the internet.

Then again, seeing that the amp was turned on with the output transistors not attached to a heatsink, there has been a massive replacement of parts, etc.

[g1]

Probably time to remove output transistors, check them out of circuit, and see what kind of supply voltages are there with them removed.

[Valvehead]

A different post had arrived at a 100 watt lamp.

Even so, the last go round without the limiter, the mains fuse blew immediately.

Whatever is wrong, it sure is not obvious across the internet.

Then again, seeing that the amp was turned on with the output transistors not attached to a heatsink, there has been a massive replacement of parts, etc.

with those up off the heat sink.. i would power on just long enough to look at the bulb, or quickly take a measurement. Never have it on more than 3 to 5 seconds

[Jazz P Bass]

I for one am at a loss.

[Valvehead]

i will pull the 3 chips tonight and test them , plus see what voltage is at the holes

[Valvehead]

question...
should i pull 1 at a time , measure and put it back in...then move to next ?

or pull all 3 to measure ?

on a side note.. so far .i pulled tr10 and have no short

[Jazz P Bass]

Well, I guess that can be considered progress (TR10 out, no short)

At this point, TR10 out, I would measure the base voltages of the output transistors.

Both bases should be very slightly on. (.500 Vdc)

In the past I have removed output transistors & installed a 1K/ 2 watt resistor from base to emitter, for troubleshooting voltages .

[Valvehead]

base of tr8 +24v

base of tr9 +21v

[Valvehead]

with tr10 out....

i get this , b/c/e

tr8 +24 / +38 /+ 37
tr9 +21/ +24 / +20

[Jazz P Bass]

21 volts on the base of an output transistor is silly.

Tr7 & TR4 voltage readings may help explain things.

For now, I would remove TR9.

If you have them, install a 1K/ 2w resistor on base/emitter TR9 & 10.
Leave the transistors out.
If you have not already, remove the limiter.

[Valvehead]

ok ,,for now i did this =

removed tr9.

so tr9/10 are out , tr8 still in.

i removed the current limiter

still have +40vdc at the speaker jack

measuring b c e

tr8 +27 / +41 / +40

tr9 holes -18v / +26 / -35

tr10 holes -35 / -31 / +39

[Jazz P Bass]

TR7 & 4 voltages.