50 watt fire up

[Trem Abuser]

OK, with baited breath, I plug it in and turn it on. First thing to check heater voltages. Each socket reading 3.22 VAC. George's instructions state 3.35 VAC. Will mine be enough for the tubes?

Next, flip the standby switch and measure pin 3 on the output tubes. Reading 468 VDC (scary, I had one hand behind my back, but I was still leery of such high voltage).

Discharged the one filter cap which is not under the board, and installed the preamp tubes. I got some strange readings which I want to check with you guys before going any further on the amp.

Here is the list by tube, pin # and measured voltage:

V1 (#1 = 154V, #3 = 1.15V, #6 = 210V, #8 = 2.24V)
V2 (#1 = -0.41V, #2 = -0.43V, #3 = 1.4mV, #6 = 315V, #7 = 1.5mV, #8 = 142V)
V3 (#1 = 348V, #2 = 23.1V, #3 = 31.6V, #6 = 184.5V, #7 = 15.7V, #8 = 26.2)

Some of my numbers were no where near the numbers listed on the charts, and I can't believe that is a good sign. For instance, my amp has no wire on V2, pin #1, so I do not see how it could have 140-150 volts on it.

Any help or suggestions would be appreciated.

Scott

[Billy Batz]

OK, with baited breath, I plug it in and turn it on. First thing to check heater voltages. Each socket reading 3.22 VAC. George's instructions state 3.35 VAC. Will mine be enough for the tubes?

Next, flip the standby switch and measure pin 3 on the output tubes. Reading 468 VDC (scary, I had one hand behind my back, but I was still leery of such high voltage).

Discharged the one filter cap which is not under the board, and installed the preamp tubes. I got some strange readings which I want to check with you guys before going any further on the amp.

Here is the list by tube, pin # and measured voltage:

V1 (#1 = 154V, #3 = 1.15V, #6 = 210V, #8 = 2.24V)
V2 (#1 = -0.41V, #2 = -0.43V, #3 = 1.4mV, #6 = 315V, #7 = 1.5mV, #8 = 142V)
V3 (#1 = 348V, #2 = 23.1V, #3 = 31.6V, #6 = 184.5V, #7 = 15.7V, #8 = 26.2)

Some of my numbers were no where near the numbers listed on the charts, and I can't believe that is a good sign. For instance, my amp has no wire on V2, pin #1, so I do not see how it could have 140-150 volts on it.

Any help or suggestions would be appreciated.

Scott

V2 Pin1 has the voltage from pin 6 comming by way of a resistor right?

[Trem Abuser]

Dan, there is no wire at all connected to V2, pin 1. The wiring diagram I showed no wire connecting to V2, pin 1, so I'm not sure if this answers your question or not.

Is my wiring not correct?

[Billy Batz]

But you have the resistor going from V2pin 6 to V2 pin 1 right? If you dont you should. Theres a 100W resistor that goes between pin 6 and pin 1 of V2 then you bend a leg of the resistor around to directly jump pin 1 and pin 7.

[videocat23]

"Theres a 100W resistor that goes between pin 6 and pin 1 of V2 then you bend a leg of the resistor around to directly jump pin 1 and pin 7."

you mean 100 ohm 1 watt

[Trem Abuser]

I did not have that resistor; I didn't realize I needed it.

I'll go get one, put it in, and then re-measure all my voltages.

Thanks Dan.

[Billy Batz]

Look closely on your metro CD.

[Billy Batz]

"Theres a 100W resistor that goes between pin 6 and pin 1 of V2 then you bend a leg of the resistor around to directly jump pin 1 and pin 7."

you mean 100 ohm 1 watt

No I meant 100k. Whoops

[Trem Abuser]

Thanks for catching that Dan, I'll get a 100k resistor.

I thought I did look closely at the CD - what page are you referring to that shows the resistor?

[Guest]

Look at step 15 on the 100 Watt Amp Kit Step by Step Pdf.

Dax

[Trem Abuser]

OK, installed the 100k 1/2 watt (Radio Shack had no 1 watt resistors and no place else open on a Sunday night) resistor across V2, pins 1 and 6, and a section of buss wire from pins 1 to 7. Here are the new readings:

V1 (pin#1 = 146.5V, pin#3 = 0.97V, pin#6 = 192V, pin#8 = 1.91V)
V2 (pin#1 = 164V, pin #3 = 0.97V, pin#6 = 282V, pin#7 = 164V, pin#8 = 165V)
V3 (pin#1 = 327V, pin#3 = 29.5V, pin#6 = 175V, pin#8 = 24.5V)

I then installed the power tubes and read a reading of 0.37V before the 2A fuse blew. I then put another 2A fuse in and tried again. It blew also. Both fuses went about about 10 seconds after I throw the standby switch before they give up the ghost.

I'm lost. Any ideas on how I should proceed?

[Trem Abuser]

Look at step 15 on the 100 Watt Amp Kit Step by Step Pdf.

Dax

OK, I see it now. I missed it as I was mostly referring to the wiring guides, and had not looked at the 100 watt kit instructions for a while.

Thanks

[Flames1950]

OK, installed the 100k 1/2 watt (Radio Shack had no 1 watt resistors and no place else open on a Sunday night) resistor across V2, pins 1 and 6, and a section of buss wire from pins 1 to 7. Here are the new readings:

V1 (pin#1 = 146.5V, pin#3 = 0.97V, pin#6 = 192V, pin#8 = 1.91V)
V2 (pin#1 = 164V, pin #3 = 0.97V, pin#6 = 282V, pin#7 = 164V, pin#8 = 165V)
V3 (pin#1 = 327V, pin#3 = 29.5V, pin#6 = 175V, pin#8 = 24.5V)

I then installed the power tubes and read a reading of 0.37V before the 2A fuse blew. I then put another 2A fuse in and tried again. It blew also. Both fuses went about about 10 seconds after I throw the standby switch before they give up the ghost.

I'm lost. Any ideas on how I should proceed?

Both my 50 watt Marshalls use a 3 amp fuse for the mains.......and I usually use slo-blo's, although George's stuff typically comes with fast blow fuses. I'd try a three amp slo-blo, but absolutely nothing bigger (this ended up getting the Heyboer 50 watt PT, right?) If it still pops the 3 amp I'd try a known good pair of tubes if you haven't already.

[Flames1950]

Also check the plate resistors on V3, the phase inverter. I don't think you should have that wide a variance between pin 1 and pin 6. Should only differ by maybe 10% at the most. It's the 82K and 100K resistors in a "V" on the board, pull the V3 tube and you should be able to read the resistor values without removing them from the board.

[Trem Abuser]

Thanks Flames, I'll try that.

Yes, I did get the Heyboer.