Ye Olde Vox Kensington Amp Quandry

[g1]

Is there something on the board that says which is Q1, Q2, etc.? One pin (collector) of Q1 goes to the 18V.

Is this a Kensington Bass V1241 ? That is the schematic we are looking at.

[fdesalvo]

Is there something on the board that says which is Q1, Q2, etc.? One pin (collector) of Q1 goes to the 18V.

Is this a Kensington Bass V1241 ? That is the schematic we are looking at.

Edit: If I ground c4 and r8 directly, I get full volume. The amp came to me as the chassis separated from the cab, which I've discovered houses the other end of the "G tuner" assembly. c4/r8 ground through a 2.7kr located on this remote board, which is connected via a 3 pin molex connector. Green = ground here. Looks like the answer to this riddle is the customer cannot play this bass without the g-tuner connected, since what we will assume is the emitter based upon the schematic, is just floating without a ground. I'll get the cab and will confirm.

the It’s the 1241 with “g tuner”. There are no markings on the board, so I’ve been indexing against the pin connections from the B+ rail or tracing from the input on the schematic.

[fdesalvo]

LOL!!

I grabbed the cab and lo/behold, the sub board is perched on a little triangle of wood upon the inner rear cab panel. After plugging in the harness, I was greeted to what sounded like a WWII era air raid siren - in the key of G. Switching off the g-tuner system silenced this tone and the damn thing plays. I've learned some lessons here, namely customers don't tell you the full story. I've also learned about troubleshooting transistors and now have some fun test tools to play with. I can't thank you all enough lol.

[g1]

I think when you were injecting signal it must have been big enough to somehow get around Q2 being turned off, probably quite high level.
I would suggest you calibrate your test set up so you can inject a signal that is somewhere around guitar level.

[fdesalvo]

I think when you were injecting signal it must have been big enough to somehow get around Q2 being turned off, probably quite high level.
I would suggest you calibrate your test set up so you can inject a signal that is somewhere around guitar level.

For certain. I’ll have to sort that out. Appreciate you guys.

[g1]

A good general purpose signal level for instrument level inputs is 50 millivolts RMS (.05V)

Attaching a 1 piece version of the Vox Kensington schematic.

[fdesalvo]

10.5vac was being injected. I can’t get my daw to push less than .2vac. I think that’ll do if like level is around a volt.