The Amp Garage

I'm late to this party and I'm an amateur. I've built about 15 amps and done a decent amount of trouble shooting. Take what I say with a grain of salt. My general sense is that good diagnostic technique starts with the basics. Reading through, this is what I think we have as cogent facts: 1) There'...

What AC voltage reading are you getting feeding the rectifier? (345-0-345 on the layout) Clip one meter lead to ground, set to AC and measure each leg going into the diodes with the amp in standby It was 372 and 373, as well as a 52v reading from the 50v PT output, which was right before the HT fus...

http://www.ceriatone.com/ceriatone/wp-content/uploads/2016/08/OTSFM50-ModernEagleMod.jpg This my layout. I modded the slope and one other resistor by a stacking parallel resistor on it. Other than that, my model does not have a half power switch and I used Magnetic Component Classic Tone trannies. ...

Is your power transformer getting hot ? Next pull your power tubes and recheck voltages make sure you don't have a weak ground I got a bad batch of Belton octal tube sockets in the past. I will never use them ever. They were shorting out inside the socket. I was at my wits end on that issue thanks ...

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#1 check your bias then voltage chart the amp starting at B+1 to V-1 The voltages are all over the place.... First, the one that seems okay... The wall voltage measured at main switch: 122.4. At least it's at a good level no matter if it's clean or not. The first voltage... Bias: 2.9 and 3.6 respec...

Are you having the same trouble with both amps? Bad, post-Irma wall current? If it's not an external issue, I would suspect the filter caps. You can measure ripple AC on the HT, and (if SS rectified) you can just clip in an additional 40uF at the reservoir to see if it reduces hum. Not related or q...

All, Well, I survived Hurricane Irma's 100 mph gust and two feet of rain, but this new problem with my Ceriatone FM50ME may be stressing me out even more than two days and nights without power and A/C. I have a church gig starting at 2pm Saturday and need this amp.... My back-up Bill M Blues Jr also...

Yeah, I doubt that these tubes will last all that long. I'll replace the tubes a whole lot sooner going forward. The meter will tell the difference. The amp sounds great after another 20+ hours of tube burn-in. The amp has got more bloom now than EVER. I'm getting some very musical bloom at conversa...

I've had mixed experience with so-called matched tubes. If they are within a couple of mA that's reasonable (5%). Never bought burned-in matched though. I'd put a few hours on them and recheck the bias. So, in checking the bias this evening before I put it back in the cab, I have 37.1 and 37.3 resp...

Hours? It was "on" at least 3,500. Maybe as many as 6,000. It is actually about 5.5 years since I last had it on the bench... Almost three straight years of that was every weekend (50+ per year), plus some time during each week. Pretty impressive reliability there. Is this one you built, or did Cer...

Thanks for the feedback.

Yeah, the first PI adjustment was noteworthy too, as you might expect. Using Gil's method, I bounced back and forth over parity three times. I'm within 1-2V. This too will likely change a bit as the tubes burn-in anyway. It's still outside the cab for a reason...

Two new, matched Mullards 6L6GCs are now in.... I have V4 at 37.7 and V5 at 39.2. Is a 1.5 difference with new tubes fairly normal? Some tube rolling helped the tone a little before the new tubes arrived. The Sovtek 12AX7LPSs from V1 and V2 are now in the PI and the CLator. The JJ 12AX7 Gold Pin fro...

Hours? It was "on" at least 3,500. Maybe as many as 6,000. It is actually about 5.5 years since I last had it on the bench... Almost three straight years of that was every weekend (50+ per year), plus some time during each week. So, 16+ hours weekly each of those years. Since then, I'd say probably ...

All, I just pulled my Ceriatone OTS50 #102 (Modern Eagle Mod) out of the cab for the first time in five years to service and update a couple of things. I checked some voltages and the bias, and I got an odd reading. My checks of Pins 4 and 5 on the two "matched" Winged C 6L6GCs were 498V and -44.6V/...