The Amp Garage

You could be measuring through the grid resistors attached to the PI caps, thorugh the PS, back thorugh the HT PS through the anode resistor of the PI and back to the other side of the coupling cap.

I'd expect both caps to read the same.

You get your unit back from UL, but the catch is that if it fails you have to take a corrective action and re-submit for a new test and pay the same fee again. I've been to U.L. (Raleigh NC) for Pilot Duty testing of a solid state output before and I think it cost something like $1500 for the one da...

It appears that the appropriate UL document is UL 60065, second in this list: http://ulstandardsinfonet.ul.com/catalog/policystandards.html It is based on the IEC specification IEC60065 which is the Harmonizing document for international agreement. http://www.sirim.my/iscs/tcA/iec60065%7Bed7.1%7Den_...

It appears that the appropriate UL document is UL 60065, second in this list: http://ulstandardsinfonet.ul.com/catalog/policystandards.html It is based on the IEC specification IEC60065 which is the Harmonizing document for international agreement. http://www.sirim.my/iscs/tcA/iec60065%7Bed7.1%7Den_...

Here in NE Tennessee we have been getting snow regularly since Dec. 1st. Deepest accumulation so far has been 8"(20.5cM), but in the mountains not far from here they are getting much more. I had a difficult time getting out of the driveway today as it is uphill the last 40' or so with a climb of ove...

I would venture that it depends on the amplifier stability. An unconditionally stable amp should have no problems. If the amp is not unconditionally stable, it could break into oscillation when the load impedance changes to a very high state. This would be the equivalent of being driven with no load...

I'll take aonther look at Fender. I saw several products with FCC class B (EMI/EMC) but didn't notice CSA on them. cULus is the same way. If you have it (UL rating) it is recognized in Canada, etc. For instance, the Frontman 65R manual (2007, P/N 763CAX008 REV A) shows CE and C-Tick, but no safety a...

OK, anyone have something manufactured in the last ten years?

I posted this in one of the Dumble threads, but for those of you who don't read them I'll post it here too. We have a Safety Engineer on site who interfaces to all the agencys for our products. He volenteered to check all the UL files he has access to and he can not find a single tube amplifier list...

I had our local Safety guy check the UL files he has access to and he can not find a single tube amplifier listed!

I've also started checking Fender and other manuals and find no UL listings.

Can anyone produce documentation of a tube amp with UL Certification?

Control the screen voltage with a variable supply. single knob controls all the screens with the tube pairs controlled in opposite directions. Increase one set of screens while decreasing the other set.

X caps are safety agency rated line to ground and are supposed to be non-shorting capacitors. Generally they are MKT and occasionally MKP. Y caps are safety agency rated for line to line application and must fail open as well. (In Europe the lines can be delta or Y connected mains, and electrically ...

To correctly phrase what I was trying to say, in class AB neither tube may go into cutoff at low output levels (similar to class A), while at higher levels both tubes will spend part of their time in cutoff. This distinction is improtant because there is a difference in distortion profile between th...

Vishay makes the standard 418P series in 400V. They are not carried by any vendors I've been able to locate and I suspect his is what Z uses, and he has to special order them.

http://www.vishay.com/docs/42017/42017.pdf

I would replace all the Al Electrolytic caps, including those on the preamp and driver boards.

The blue film cap from the power switch to the chassis is a holdover from a two wire design and may be an issue as well. I've seen them trip GFIs as well as causing hum problems.