Deluxe Reverb problem

[tyler8611]

I just built a DR, I connected C and D to a copper preamp ground bus, and the first three caps to chassis next to the PT. Mine is as quiet as a mouse.

I'll certainly have to try it. And I need to verify the pots are working correctly. I've tried about everything else.

[tyler8611]

I'll certainly have to try it. And I need to verify the pots are working correctly. I've tried about everything else.

Tried it- no difference. Resoldered everything. V4 had 170v and 160v on the plates. Reverb red center tap: 395v. Cathode 1.3. Only thing I havent checked is the heater wiring from that tube. Touched up the joints but the pair could be shorted.

[tyler8611]

I just built a DR, I connected C and D to a copper preamp ground bus, and the first three caps to chassis next to the PT. Mine is as quiet as a mouse.

Where did you ground the copper bus? Mine is near the input. It turns out I already had the grounds wired the way you're describing. First two stages to the center tap ground, others to the buss. So unless the opposite may be true for my amp, I have no idea what's causing this.

[pdf64]

It may be helpful to record a clip of the motorboating issue, along with the effect adjusting any controls may have on it. Upload to youtube etc and provide a link.

[tyler8611]

It may be helpful to record a clip of the motorboating issue, along with the effect adjusting any controls may have on it. Upload to youtube etc and provide a link.

Good idea.

[tyler8611]

I thought I'd had it traced down to the fact that my V4 to V5 heater pair was out of phase, but correcting that didn't cure it. All I have left to try is the V3 to V4 pair, which checks out good on continuity.

[pdf64]

With a balanced heater system, there a tiny theoretical benefit from arranging p-p power tube heaters in like polarity, but for the rest of the amp, I think it's immaterial; rather the guideline of lining up heater polarity for all the sockets seems akin to a good luck charm that everyone clings to because they don't want their amp to hum
As there's a global NFB loop, the LTP phase splitter is really part of the power amp.
To help get your head around HT - 0V hum considerations, see The Valve Wizard
BF 0V arrangements are kinda random really, the fact that generally it works well may have been down to trial and error and good luck; hence it may be a good idea to review where your amp's 0V arrangement differs from a real BF.

[tyler8611]

With a balanced heater system, there a tiny theoretical benefit from arranging p-p power tube heaters in like polarity, but for the rest of the amp, I think it's immaterial; rather the guideline of lining up heater polarity for all the sockets seems akin to a good luck charm that everyone clings to because they don't want their amp to hum
As there's a global NFB loop, the LTP phase splitter is really part of the power amp.
To help get your head around HT - 0V hum considerations, see The Valve Wizard
BF 0V arrangements are kinda random really, the fact that generally it works well may have been down to trial and error and good luck; hence it may be a good idea to review where your amp's 0V arrangement differs from a real BF.

Thanks I'll look into this.

[g1]

Pin 8: 15.9 mA (64.2 mV)
. 16.2 mA (65 mV)

Sorry to go back to the bias thing again, but these readings don't make sense. And the mV reading for a 1 ohm cathode resistor indicate a very hot bias that may explain why the pin5 voltage is so far from norm (-20V vs -35V)
Heavy loading of the supply could also account for other odd issues.

How are you doing the current measurement (mA) ? Are you disconnecting the cathode resistor to do it?
Are the cathode resistors actually 1 ohm and do you measure around 65mV across each at idle with no signal?

[tyler8611]

Sorry to go back to the bias thing again, but these readings don't make sense. And the mV reading for a 1 ohm cathode resistor indicate a very hot bias that may explain why the pin5 voltage is so far from norm (-20V vs -35V)
Heavy loading of the supply could also account for other odd issues.

How are you doing the current measurement (mA) ? Are you disconnecting the cathode resistor to do it?
Are the cathode resistors actually 1 ohm and do you measure around 65mV across each at idle with no signal?

Yes I'm measuring at idle, no signal. Not disconnecting. They are definitely 1 ohm and soldered between pin 8 and grounding tabs. These are the readings I get. Meter set to lowest range on both mA and mV (200).

[tyler8611]

Just a reminder, the normal channel plays fine with V4 removed. The rumbling goes away. But no sound from vib channel at any setting.

[tyler8611]

Sorry to go back to the bias thing again, but these readings don't make sense. And the mV reading for a 1 ohm cathode resistor indicate a very hot bias that may explain why the pin5 voltage is so far from norm (-20V vs -35V)
Heavy loading of the supply could also account for other odd issues.

How are you doing the current measurement (mA) ? Are you disconnecting the cathode resistor to do it?
Are the cathode resistors actually 1 ohm and do you measure around 65mV across each at idle with no signal?

What's the typical range for mV across the resistor?

[tyler8611]

I've recorded it but I don't know how to post it on here.

[tyler8611]

I had hooked it up to a different speaker that I could hear better. Definitely motorboating.

[g1]

You have to disconnect the cathode resistor if you want to measure mA current directly. Current measurement must be done with the meter in series. The point of having the 1 ohm cathode resistors is so you don't have to 'break in' to the circuit and can just measure voltage in mV across the resistor.
So your mA numbers are not valid. Your measurement of 65mV across the resistor is what you should go by. 65mV divided by 1 ohm equals 65mA idle current. At 400V plate, you are idling those tubes around 26watts. If you are lucky they may still be ok.
Somewhere around 20mA is probably more appropriate, which will measure as 20mV across the 1 ohm resistor.