ODS 124 PCB Build

[professormudd]

I recorded 14.5R and 13.5R. Amp off, unplugged, tubes in...

...I did your procedure as follows:

13.5R, 40mA (13.5 x .004) = 0.054, giving me .108 per side.

I only have one bias pot on this amp. Clipped my common lead to the standby switch, clipped other lead to pin 3. Everything was turned all the way down and I adjusted the pot until I got around .108.

You're off by a factor of ten. You want to see 1.08 volts across the 13.5Ω side of the OT.

Maybe that's why I shouldn't be doing this at 4:00 in the morning. Stupid question should I be measuring AC or DC in that case?

[martin manning]

DC. You're just using the DC resistance of the OT primary in place of the 1Ω current sensing resistors on the cathodes. Note you'll get plate current only using this method, so I'd target about 55% of Pd max (which is 30W for 6L6GC). That's 0.55*30W/450V = 37mA, so set 2*0.037A*13.5Ω = 0.999V on that side. After you've done that, check the B+ to see if the estimate of 450V at idle was good.

[professormudd]

DC. You're just using the DC resistance of the OT primary in place of the 1Ω current sensing resistors on the cathodes. Note you'll get plate current only using this method, so I'd target about 55% of Pd max (which is 30W for 6L6GC). That's 0.55*30W/450V = 37mA, so set 2*0.037A*13.5Ω = 0.999V on that side. After you've done that, check the B+ to see if the estimate of 450V at idle was good.

The idle was 457 volts. So then I would get 36mA. Which comes out to .975 volts.

I will set that value. Thank you.

[professormudd]

Okay I got that value set. I still have the hum issue that I'm looking to figure out as well as the PAB and OD relays not working.

Does anyone have suggestions as to what to check?

[xtian]

Okay I got that value set. I still have the hum issue that I'm looking to figure out as well as the PAB and OD relays not working.

Does anyone have suggestions as to what to check?

You said you confirmed 12vDC for relays. Are the relays actually functioning? When you flip your switches, can you hear the relays click? Use your multimeter to confirm conductivity of relay terminals in open and closed positions.

[professormudd]

Okay I got that value set. I still have the hum issue that I'm looking to figure out as well as the PAB and OD relays not working.

Does anyone have suggestions as to what to check?

You said you confirmed 12vDC for relays. Are the relays actually functioning? When you flip your switches, can you hear the relays click? Use your multimeter to confirm conductivity of relay terminals in open and closed positions.

I did confirm 12vdc on the relays at the diodes. The side with the stripe, closest the the front of the chassis reads 12.07vdc consistently. The other end of each diode reads 12.07vdc when the switch is set to pedall, 0.5mVDC when manual. I cannot hear either relay click. I do not get a change in continuity either. I believe the switches are fine. I wonder if my relays were not the right ones.

[Richard1001]

You have latching relay's. This means that the relay switches when you apply a voltage pulse and stay's in the same position untill you apply a pulse with reversed polarity.

You need a non-latching relay that switches if there is a voltage applied and switches back when the voltage is cut off.

[professormudd]

You have latching relay's. This means that the relay switches when you apply a voltage pulse and stay's in the same position untill you apply a pulse with reversed polarity.

You need a non-latching relay that switches if there is a voltage applied and switches back when the voltage is cut off.

Thank you for the reply.

Will these work?

https://www.mouser.com/ProductDetail/om ... cycode=USD

[xtian]

Will these work?

https://www.mouser.com/ProductDetail/om ... cycode=USD

That looks right to me. Others will confirm.

[Richard1001]

Yes, these will work.

[professormudd]

Cool. Looking forward to figuring out how to install these with the board wired in. I got the old ones out, but the holes have a little solder in em. Not sure how to properly empty these tiny holes to make room for the pins.

[xtian]

Solder sucker. Don't have one yet?

https://www.amazon.com/EDSYN-The-Origin ... 006GOKVKI/

[Richard1001]

https://youtu.be/HZLQzBOOQbw

[pompeiisneaks]

This is my favorite one:

https://www.amazon.com/Engineer-SS-02-S ... 907&sr=8-4

comes with silicone tip instead of plastic so it lasts a ton longer.

Any of them do the job though.

~Phil

[Richard1001]

Also: have you wired the diode that's on the relay the right way? It looks like the anode is wired to the red wire and if red represents positive, the diode needs to be reversed. The diode over the relay coil needs to be in reverse: anode to ground and cathode to positive.