The Amp Garage

Been playing “Operation” with the main board for the last couple hours and I’m getting close to being at the next test point. I was hoping to get some feedback on the PI lead dress if possible before I nail it. Took a gander at the Livesey site and the documented Bluesmaster builds here - most notab...

martin manning wrote: ↑Wed May 15, 2024 2:16 pm Yea, sorry for the diversion. If you went ahead and wired the rest of it up you'd have been fine. Hopefully the learning was worth the trip!

Always worth it Martin; and appreciated

sluckey wrote: ↑Wed May 15, 2024 3:50 am Sorry for the filament string wild goose chase. I missed you saying you had correct voltage between the filament pins.

No worries! I appreciate any feedback and any opportunity to learn. It’s all very good

I’ll have to look and see. If so - shame on me for forgetting that lesson. I can still remember the serial number of every weapon that was ever assigned to me (going back ~30 years now), but I can’t remember what I ate for dinner 3 days ago. Age, TBIs, too much Laphroaig, all of the above? :lol: Onw...

Do you have heater leads connected between the two sockets? If not that would explain it. I thought I saw a back/white twisted pair. I added the twisted pair late last night to perform sluckey’s test; but they weren’t soldered in to V4. I was measuring from the loose leads. I took them out a little...

martin manning wrote: ↑Wed May 15, 2024 1:45 pm That says that the 150R from 2 isn't connected to ground.

I’ve actually got that resistor on pin 2 of V4. Should I move it or connect the heater bridge and see if the voltage balances out?

Measuring across the two heater leads coming out of the transformer with the bulb limiter in place gives me 6.4vac.

Understood.
I get 150 from 7 to ground, but open from 2 to ground. When the heater leads were attached, I was getting 150 on either/both sides. Here’s a close up of the socket:

I’ve got the ACT, bias pot resistor, and ground wire from the bias supply board all sharing the same ground lug. Pin 7 has the 150R ACT, the blue wire to the resistor side of the LED terminal strip, and a green heater wire. If I detach the heater leads and measure across them, aren’t I essentially r...

I’ll go over everything one more time, but I’m fairly certain that I don’t. Is it safe to measure heater voltage with the leads off the socket and just hanging in the air? The only other thing I wonder about is the terminal strip where the LED connects. Could the phenolic part have absorbed flux and...

One thing I noticed was having the diode and resistor for the lamp going to the wrong pins - so I fixed that. Measuring as sluckey advises gets me 6.4vac and has always been right around that. It’s when I measure each pin to ground that I get the stated discrepancy. If measuring that way isn’t relia...

Understood and thank you for the advice

Currently retracing everything and will report back.

Ok, replaced the heater ACTs with 150R and fired it up. Now I have 6.2vac on pin 2 and 0 on pin 7.

Could the PT wires have been incorrectly marked? The clipped/wrapped heater CT has the white stripe on it and the two I’ve got going to V5 are solid green.

What else could it be?

Ugh! It appears that I do indeed. I guess that would explain it. I suppose it wouldn’t be one of my builds without a stupid mistake like this, lol. Hopefully I can limit it to just this one… I have a Mouser bag sitting here with 2 Koa 150R resistors in it that for the life of me I couldn’t remember ...

“ Don't understand this... If pin 2 to pin 7 is 6.2, I would think pins 2 and 7 should both be ~3.1 to ground. Is the only load you have on the heater circuit the panel lamp? What kind of panel lamp is it?” I thought that was odd… The panel LED strip is wired per the layout with the 1n4003 and a 511...