Buick (I mean) Randall Century 170 II LOW output and no drive.

[Indyryder02]

No. I don’t think either are identical to the century 170 II
but closest I was able to find, and the notated one at least helped discuss it easier.

[Indyryder02]

I’ll update once I get the replacements in. Hopefully that will be the fix. The power amp didn’t seem to have full output either when I put signal into the return. So may be more to figure out still. But I hope for the best for now!

[Indyryder02]

The new JFETS got it up and running again.

It has a bias adjustment but no spec for what it should be.
Any suggestions?
I did measure across the emitter resistors..
it was already set at its maximum. About 50mv across the .6 resistors. And can go as low as about .5mv
No crossover distortion regardless of setting.

<20mv dc offset

[g1]

I did measure across the emitter resistors..
it was already set at its maximum. About 50mv across the .6 resistors. And can go as low as about .5mv
No crossover distortion regardless of setting.

If there is no crossover, I would set for minimum. Measure across the 0.27 ohm emitter resistors of the final outputs. 5mV across 0.27 is around 20mA which is easily sufficient. 50mV across 0.27 would be closer to 200mA idle current, which is way too high.

[Indyryder02]

If there is no crossover, I would set for minimum. Measure across the 0.27 ohm emitter resistors of the final outputs. 5mV across 0.27 is around 20mA which is easily sufficient. 50mV across 0.27 would be closer to 200mA idle current, which is way too high.

Only has the .6 final emitter resistors (not the c1000 model) but I see what you’re saying. That’s the info I needed. Thank you! Seems it must be designed to prevent any setting that would harm it, thankfully. Since it was at max when I got it!

[Marcio_Luthier_Brasil]

No. I don’t think either are identical to the century 170 II
but closest I was able to find, and the notated one at least helped discuss it easier.

Hello, I was the one who made the notes on the RG 170 circuit, the confusion between Jfets Q3 and Q4 and that I changed the design according to the RG170 I board, the RG 170II is a little different, but the fact is that in both modes both the RG 170I and 170II designs work to mute the "Green" Clean channel and I'll tell you one more thing this RG170I amplifier was poorly designed, the bleeding problem from the other Topic was only solved by adding an extra gain stage after the "Gain voycing" of the amplifier, any questions I'm here to help.

[Marcio_Luthier_Brasil]

Only has the .6 final emitter resistors (not the c1000 model) but I see what you’re saying. That’s the info I needed. Thank you! Seems it must be designed to prevent any setting that would harm it, thankfully. Since it was at max when I got it!

Please, if you can, send me a photo below the plate so I can see and readjust the layout for the Rg 170II, thank you

[Indyryder02]

Please, if you can, send me a photo below the plate so I can see and readjust the layout for the Rg 170II, thank you

Don’t have the amp anymore. It’s back rocking on the road again.

[Marcio_Luthier_Brasil]

I researched the configurations of the randall's rg 170 and century 170ii, i found at least 2 configurations of each model, with different output impedances and subtle changes in the pre, so i re-did this schematic for the century170ii,IF ANYONE WANTS THE SCHEMATICAL, JUST SEND ME AN EMAIL TO musimarcio@gmail.com