Bias problems---

[SoulFetish]

Ok... i just got back from vacation last night. Ready for the madness ? I powered it up to test just now .... and now I have 15 vdc at the grids of V6-7 and 0vdc at v8-9................yep !

Well I’d say that’s progress! Only thing is you came back from vacation a little early. Go away for another two days or so, then come back and those voltages should be right we need them to be.

[Valvehead]

Absolutely stumped here....

I did a hail mary and installed some new caps and resistors tonight ..i dont know what else to do at this point ? I cleaned the sockets and pcb with alcohol and contact cleaner..i dont see anything wrong anywhere. No cracked joints or lifted traces...no solder blobs or hairs .

So everything from the out of the plates of V5 is brand new ....also replaced R3 / c3 / c4 . All grounds check good . Ive worked through the circuit checking continuity .


same result = V6/7 super high volts ............v8/9 nothing .

[glebert]

Well I’d say that’s progress! Only thing is you came back from vacation a little early. Go away for another two days or so, then come back and those voltages should be right we need them to be.

I think Mercury is in retrograde until Sunday. Still needs two more days.

[Jazz P Bass]

"Absolutely stumped here...."

It appears that the PCB itself is bad.

Have you tried contacting Orange for a replacement?

[Valvehead]

"Absolutely stumped here...."

It appears that the PCB itself is bad.

Have you tried contacting Orange for a replacement?

no, but i can try that

[Helmholtz]

Did anyone notice the strange "inverse operation" of V2-B and V4-B in the schematic? I wouldn't trust this sloppy diagram.

[Valvehead]

More testing today = with all tubes removed

from the el84 area and after , to the OT and jacks , all continuity is ok

plates at 360v

2 test points are not right at pin3 - should be 9-12v according to scem but i get=
v6 5mv
v7 0 v
v8 5mv
v9 0 v

grounds check good , all speaker jacks getting to ground

R84 tests around 0 ohms in circuit and no matter where the half pwr/ full pwr / standby switch is set = its going right to ground , both ends . But it tests 100k out of circuit??

if something was wrong with C47 or C48 , could that cause the mayhem ??

[doombass]

R84 tests around 0 ohms in circuit and no matter where the half pwr/ full pwr / standby switch is set = its going right to ground , both ends . But it tests 100k out of circuit??

if something was wrong with C47 or C48 , could that cause the mayhem ??

If you disconnect what I recon is a quick connector SW9. Still 0 Ohms to ground? If yes, disconnect SW8. Still 0 Ohms to ground?

[Helmholtz]

More testing today = with all tubes removed

from the el84 area and after , to the OT and jacks , all continuity is ok

plates at 360v

2 test points are not right at pin3 - should be 9-12v according to scem but i get=
v6 5mv
v7 0 v
v8 5mv
v9 0 v

grounds check good , all speaker jacks getting to ground

if something was wrong with C47 or C48 , could that cause the mayhem ??

With all tubes removed there is no current through R83/85 and TP10/TP11 should have 0 V.

I did not read all the posts, but can you exclude a conductive V6 socket? If you disconnect the 2k2 grid stopper resistor directly at the V6 socket, what voltage do you measure at open pin 2 (tubes pulled)?

[doombass]

With all tubes removed there is no current through R83/85 and TP10/TP11 should have 0 V.

I did not read all the posts, but can you exclude a conductive V6 socket? If you disconnect the 2k2 grid stopper resistor directly at the V6 socket, what voltage do you measure at open pin 2 (tubes pulled)?

Answer in reply #18. 0V when grid stopper resistors are lifted.

[Valvehead]

If you disconnect what I recon is a quick connector SW9. Still 0 Ohms to ground? If yes, disconnect SW8. Still 0 Ohms to ground?

the standby / half / full power is on 1 , 3 way toggle switch . 2 wires go to the trans and one wire goes to "tx8" on the pcb. With all 3 wires removed that resistor still goes to ground ... both ends

[Valvehead]

With all tubes removed there is no current through R83/85 and TP10/TP11 should have 0 V.

I did not read all the posts, but can you exclude a conductive V6 socket? If you disconnect the 2k2 grid stopper resistor directly at the V6 socket, what voltage do you measure at open pin 2 (tubes pulled)?

i just clipped that 2.2k out and i get 0v to about 1.5mv...the meter just kind of goes up and down in that range

[doombass]

the standby / half / full power is on 1 , 3 way toggle switch . 2 wires go to the trans and one wire goes to "tx8" on the pcb. With all 3 wires removed that resistor still goes to ground ... both ends

Oh, I meant the 4 tubes/2 tubes-switch which bypasses R84 to ground. In the 4 tubes setting the switch is actually supposed to short out R84 to ground.

[Valvehead]

Oh, I meant the 4 tubes/2 tubes-switch which bypasses R84 to ground. In the 4 tubes setting the switch is actually supposed to short out R84 to ground.

yes- we are talking about the same switch--r84 is going to ground on both ends , in 2 tube mode , 4 tube and even on standby

i pulled the 3 wires off it and it made no difference

[doombass]

But if we are talking about SW4_A there would be only two wires, on pin 8 and pin 9 with pin 7 not connected. Correct?