Odd V1b b+ resistor

[Jay Doherty]

Curious if anyone has come across v1 b+ resistors with values other than 100?
Photo attached shows 68k V1b b+.

Seems original and the amp appears to be untouched including filters so I assume it was a factory error. Can't find a schematic that shows any value other than the 100k. Pot codes on the amp are Dec 71 and the mustards codes are 1Q 1970 I think. 50 watt JMP Bass export. No polarity and has laydown pt.
Thanks

 

[Jon Snell]

The exact model number would be useful, save me trawling through a library of manuals.
68K anode load is recomended for ECC81 and ECC82. 82 - 100k for ECC83.

 

[Jay Doherty]

It’s a 1986. I hesitate to replace it with 100k because every solder join in the amp seems untouched.

 

[Jon Snell]

Those 68k resistors are correct, they go to the green wire which is pin 2 or pin 7. Both are grid pins not anode pins, they have blue wires.
Just notced the lurking 68k. probably helps with the clean channel as the response may be smoother with a greater load.
I would leave it as it probably enhances the sound.


Edit; Couldn't see the wood for the trees ... DOH!

 

[Purgasound]

I see the part you're talking about. Looks like a mistake. That will result in lower gain on that stage. Since those amps were hand wired there are many out there with incorrect and inconsistent values. It definitely looks original. If it sounds good then it won't hurt to leave it. Personally, I would try to source the period correct part and replace it.

 

[dtier]

Mistakes happen but it's hard to imagine that anyone could make such a glaring mistake. Maybe they were short on 100ks that day.

 

[syscokid]

The 100k Iskra 1/2 watt resistors are getting more rare by the day, which is reflected on the prices…:

https://Reverb(dot)com/item/69471152-iskra-carbon-film-0-5-watt-100k-nos

 

[Jay Doherty]

Thanks all for the info. I’ll see if I can source an original part