I have been enjoying my simple se for over a year now and wanted to get some input as to what the "right" voltage measurements should be on this board(one amp is completed and gifted to my Dad last fathers day; the second board is still bread-boarded(sigh)).
This is what I get with my Fluke:
Yellow:1= 7.94 ac, 2= 5.95 ac
Green:1=3.42 ac, 2=3.42 ac
Blue(Edcor-plate):1=448 dc, 2=448 dc
Red(Edcor-B+):1=453 dc, 2=453 dc
@560 ohm resistor:1=36.3 dc, 2=34.1 dc
Choke Input: 478 dc
Primary Red:1=402 ac, 2=402.2 ac
Wall AC: 124.8 ac
I am using the Allied 6K7VG power transformer and the big Edcor CXSE25-8-5K
Current tubes are the 6P3cE (Russian 6L6GC)
Rectifier is a Hammond labeled british made GZ34
Driver is a RCA 12AT7WA
Choke is the recommended Triad
Motor run supplemental PS cap with film bypass
Currently running in Triode mode with no negative feedback
I have inrush current limiters (CL-90) on the primary(black) and center tap(red-yellow)
My question: shouldn't there be more difference between the plate and B
+?
Also, why are the 5 volt filaments different?
Amp sounds good; these measurements have me puzzled.
This is what I get with my Fluke:
Yellow:1= 7.94 ac, 2= 5.95 ac
Green:1=3.42 ac, 2=3.42 ac
Blue(Edcor-plate):1=448 dc, 2=448 dc
Red(Edcor-B+):1=453 dc, 2=453 dc
@560 ohm resistor:1=36.3 dc, 2=34.1 dc
Choke Input: 478 dc
Primary Red:1=402 ac, 2=402.2 ac
Wall AC: 124.8 ac
I am using the Allied 6K7VG power transformer and the big Edcor CXSE25-8-5K
Current tubes are the 6P3cE (Russian 6L6GC)
Rectifier is a Hammond labeled british made GZ34
Driver is a RCA 12AT7WA
Choke is the recommended Triad
Motor run supplemental PS cap with film bypass
Currently running in Triode mode with no negative feedback
I have inrush current limiters (CL-90) on the primary(black) and center tap(red-yellow)
My question: shouldn't there be more difference between the plate and B
+?
Also, why are the 5 volt filaments different?
Amp sounds good; these measurements have me puzzled.
budmaestro said:
Based on your measurements at the cathode resistor, you've got about 65 mA running through the tube (I=V/R). You indicate a ~5 volt drop across the output transformer's primary winding. This would suggest the primary has a DC resistance of ~80 ohms (R=V/I). That is a very reasonable value for a large output transformer.
By the way, 65 mA at 450 VDC is just under thirty watts. That's quite a bit more than the 6p3s-e can handle. It really should be kept under twenty watts. I'd recommend increasing the cathode resistance (try something around 800 ohms) or look for different output tube with a higher dissipation rating (maybe some EH KT88?)
I think he's asking why the 5V winding between the two amps is so different. One is 8V and one is 6V. 8V seems really high...it this with the rectifier tube installed? Be careful, BTW, when checking the 5V filament when the rectifier is in there. Although there is only 5VAC across the winding, it will be full B+ (480VDC) with reference to ground (you).
I'm also confused about the 6.3V winding (green). Are you measuring this from the center tap? You should put the meter across the two solid green wires. Some meters don't do a very good job measuring AC, especially where there is a lot of noise on it, but the SSE doesn't rectify the 6.3VAC, so it should work fine.
I'm also confused about the 6.3V winding (green). Are you measuring this from the center tap? You should put the meter across the two solid green wires. Some meters don't do a very good job measuring AC, especially where there is a lot of noise on it, but the SSE doesn't rectify the 6.3VAC, so it should work fine.
Yes, that is my biggest concern. Do I have a bad 5v winding? Should I fix it? Seems like it would be hard on the rectifier. Amp sounds great. Better than a couple $2000 amps I got sitting idle because I like the sound of this amp. I have another power tranny,same one. I'll swap them and check again. Weekend project.
More measurements
Red face here. I did more measurements going ACROSS the filament supply wires. Noob error, I was measuring to ground. So:
6.3v fil =6.7 volts AC
5.0v fil =5.24 volts AC
Per Ty's advice I pulled the 6P3C"s and installed my favorite tube in this amp, winged C KT-88's.
I'll get some bigger resistors to get the smaller tubes dialed in closer to 40-50 mA range.
Thanx for everyones help-back to musical enjoyment and a new chassis.
PS the KT-88's are running at 73 and 75 mA respectively
Red face here. I did more measurements going ACROSS the filament supply wires. Noob error, I was measuring to ground. So:6.3v fil =6.7 volts AC
5.0v fil =5.24 volts AC
Per Ty's advice I pulled the 6P3C"s and installed my favorite tube in this amp, winged C KT-88's.
I'll get some bigger resistors to get the smaller tubes dialed in closer to 40-50 mA range.
Thanx for everyones help-back to musical enjoyment and a new chassis.
PS the KT-88's are running at 73 and 75 mA respectively
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