Fender Dlx Rev build- last Q b4 fire-up.

[Sea Chief]

Yes I want to know the voltage at pin 5 of each 6V6.
Let's do this.

1) Pull out both of the power tubes.
2) Monitor the voltage at pin 5.
3) Adjust the bias pot over its full range and report the minimum and maximum voltage readings that you get at pin 5

This will tell us if your bias power supply circuit is working properly

Ok I need to start again- completely afresh.

------------------------------------------

I read 0.01V touching the DMM probes together.

I read 1.1r touching the DMM probes together.

I have just measured (with tubes all in) at pin 5 of the 6v6 at -48v. I ascertained before that my bias tap is working & I posted the readings, by turning the bias pot, at -42V to -60v.

I have posted the plate voltages (with the new 5U4GB rectifier tube in) both of 452v.

I have added 2x 1r resisitors and measured across, with a reading of 6mV and 5.2V respectively.

[I will now do the pin 5 bias reading with both tubes pulled].

[Sea Chief]

Yes I want to know the voltage at pin 5 of each 6V6.
Let's do this.

1) Pull out both of the power tubes.
2) Monitor the voltage at pin 5.
3) Adjust the bias pot over its full range and report the minimum and maximum voltage readings that you get at pin 5

This will tell us if your bias power supply circuit is working properly

As before, it ranges from -42V to -60V. Both tubes pulled, just the power switched up (measured at pin 5 V8). Stby down.

[Tom Phillips]

...I have just measured (with tubes all in) at pin 5 of the 6v6 at -48v. I ascertained before that my bias tap is working & I posted the readings, by turning the bias pot, at -42V to -60v...

That's what I wanted to know. No need to do the pulled tube test. Your bias voltage adjustment range needs to be more like -30V to -50V to allow you to properly setup your Deluxe Reverb. The "Fix" could be just changing one resistor. We are assuming that your bias supply is the stock circuit or you think it is the stock circuit. Correct?

[Sea Chief]

That's what I wanted to know. No need to do the pulled tube test. Your bias voltage adjustment range needs to be more like -30V to -50V to allow you to properly setup your Deluxe Reverb. The "Fix" could be just changing one resistor. We are assuming that your bias supply is the stock circuit or you think it is the stock circuit. Correct?

If by stock DR circuit you are not including the PT (as you can see above the boards are DR RI).. then yes.

[Sea Chief]

That's what I wanted to know. No need to do the pulled tube test. Your bias voltage adjustment range needs to be more like -30V to -50V to allow you to properly setup your Deluxe Reverb. The "Fix" could be just changing one resistor. We are assuming that your bias supply is the stock circuit or you think it is the stock circuit. Correct?

Ive just checked R69 is as schematic 22r, and yes (well reads 23.5r with my DMM).

[Tom Phillips]

Ive just checked R69 is as schematic 22r, and yes (well reads 23.5r with my DMM).

There is no schematic posted in this thread. Please post the exact schematic you are referencing so we know what your part references are in the circuit.

[Sea Chief]

Hi Tom,

I dont know how to post it directly onto a reply here.. but in post #1 I added a hyperlink: this is to previous thread, onto which JazzP kindly added the pdf schematic.

Is that ok?

[Chuck H]

Change R59 to 6.8k

If you don't have a 6.8k you can interrupt the lead from the bias supply to the bias pot with a 3.3k resistor.

If you don't have a 3.3k resistor, what values between 1k and 10k do you have?

http://www.ampwares.com/schematics/6..._Reverb_RI.pdf

[Sea Chief]

Change R59 to 6.8k

If you don't have a 6.8k you can interrupt the lead from the bias supply to the bias pot with a 3.3k resistor.

If you don't have a 3.3k resistor, what values between 1k and 10k do you have?

http://www.ampwares.com/schematics/6..._Reverb_RI.pdf

Thanks for that link ChuckH.

Im off to dig in me box Chuck.. do I need any big fancypants 1W type again?

[Sea Chief]

Change R59 to 6.8k

If you don't have a 6.8k you can interrupt the lead from the bias supply to the bias pot with a 3.3k resistor.

If you don't have a 3.3k resistor, what values between 1k and 10k do you have?

http://www.ampwares.com/schematics/6..._Reverb_RI.pdf

Where incidentally is R59? I can see physically, but I cant find in on the pdf (you dont mean R69 do you- which is in the wee bias circuit)

[Chuck H]

R59 is the resistor between the bias adjustment pot and ground.

It occurs to me that you could just tack a 22k resistor parallel with R59 to correct it's value.

[Sea Chief]

R59 is the resistor between the bias adjustment pot and ground.

For the life of me I cant find the bias pot either!

I have a 4.7k 1/2w.

[Chuck H]

The bias adjustment circuit on the schematic is located between the PI and power tubes. But that's not important now. You know where the bias pot is physically in your amp (because you've been turning it!) R59 is the resistor that goes from that pot to ground. Tack a 22k resistor across it and you should have a more correct bias adjustment range. No special resistor needed. Whatever normal 1/2 watt resistor you have will be fine. A higher rating is ok too. It's not important for this circuit.

[Sea Chief]

The bias adjustment circuit on the schematic is located between the PI and power tubes. But that's not important now. You know where the bias pot is physically in your amp (because you've been turning it!) R59 is the resistor that goes from that pot to ground. Tack a 22k resistor across it and you should have a more correct bias adjustment range. No special resistor needed. Whatever normal 1/2 watt resistor you have will be fine. A higher rating is ok too. It's not important for this circuit.

Found it (it helps my knowledge & clearer head if I do apply myself to the schematic: here its helped my understanding of the close relationship between it, the PI and pwr tubes you see. If only a bit!).

Ok I have a 1/2W 22k and I think I can just, hopefully tack it parallel to the 1/2W as it seems too, R59 (w'out taking up board- thank feck!).

Thanks chaps.

[Sea Chief]

The bias adjustment circuit on the schematic is located between the PI and power tubes. But that's not important now. You know where the bias pot is physically in your amp (because you've been turning it!) R59 is the resistor that goes from that pot to ground. Tack a 22k resistor across it and you should have a more correct bias adjustment range. No special resistor needed. Whatever normal 1/2 watt resistor you have will be fine. A higher rating is ok too. It's not important for this circuit.

ChuckH. ive noticed s'thing odd. On the pdf R59 is a 10k. On my board it seems to be 22k.. and is indeed the same colour bands as the one I have ready to tack on (red/ red/ orange/ gold).. and also it measures (albeit in situ) 21.5k.