The Amp Garage

Replace the diodes CR11, CR12 too. If one of these went shorted or very leaky. This could pump AC into the negative power supply, with similar results to what you're reporting. 1N1003, 4004, 4005, 4006, 4007 would all work there. They all differ only in their reverse voltage rating.

If it was a car amplifier, I'd think that they estimated peak instantaneous power for a 1uS period.

If you have time to shop, make up a list of acceptable models, then haunt facebook marketplace, craigslist, etc. for some good bargains.

I got my variac (Variac brand, even!), rated at 10A, for $40 at a surplus place. Just took some waiting. Sheer luck, and knowing ahead of time what would be good.

I had to give up my bicolor indicator light on my V1 Cosmodrome in order to ground out the circuit in bypass mode because I'm unwilling to pay for a 4pdt foot switch. Use a relay. Put a Panasonic TQ-2 9V DPDT on the effect circuit board. This can make the effect itself be internally self bypassing ...

Stevem wrote: ↑Fri Oct 02, 2026 8:47 am You don’t need spec’s there so cheap just replace them both , even two 1n1007 in series on each transformer leg is fine.

Absolutely correct!!

Yep, as Helmholtz says, it works fine on chokes. I believe that in the dim mists of the 1900s, it was originally used for testing chokes and then somebody noticed that a closely-coupled transformer would do the same thing as a single choke.

Thanks for that link but I don’t have the patience for all the pop up adds that site has. Use Firefox, install AdBlocker Ultimate. It's really quite effective. I just clicked on the site. The only popup I got was a polite request to please allow ads. Apparently they try to detect ad blockers and as...

+1 on the transformer. A power rating on a transformer is only as good as the string of footnotes describing the operating conditions and frequency range. The 60W number is a capability, not a forced condition. And the "impedance" is instead a ratio assuming a slew of conditions on loading. It's eas...

I generally agree with Stevem's comments, although there are some minor bits that I would extend on. There's nothing really wrong with putting a 1N4007 in for the bias rectifier, it's just likely to be unnecessary as Stevem says. There is no tone magic there, only it needing to make a DC voltage. If...

[...] I would also say, the datasheet's recommendations are largely ignored in practice. I've seen lots of large filters on the outputs in any number of equipment, and I don't think I've ever seen the recommended capacitor discharge diode to prevent reverse voltage on shutdown actually implemented....

That's interesting information, thank you so much. The device in which the low ESR capacitors caused problems had a pair of 7805 linear regulators. That's a bit odd. The 7800 series is one of what I thought of as old-school without lot of ESR issues. I did once run into a situation where the self-i...

I'm looking for snap-in capacitors measuring 25mm diameter and 35mm height for some Laney GH series amplifiers. One of the original parts is Samwha FL and the other one is Panasonic UP, both 100µF 500V. I can't find the Samwha FL, and Panasonic UP (discontinued) datasheet does not specify ESR, so I...

No disrespect intended. Yes, if it blows fuses with just the primary connected, there is a internal problem. Telling us that would have prevented me going off like that. We get many, many people who say things like "my amp quit working - it's a dead transformer, isn't it?" with no particular reason ...

All internal fuses in the SYN-2 are fine, and there are no signs of any damage. Measurements of the power supply inputs show no short circuits on the secondary winding side. However, the primary winding reads 0 ohms (it is shorted). There is no descriptive label on the transformer. It’s a stressful...

You could use your voltmeter set to AC to measure the AC ripple voltage on each bypass capacitor. If the ripple voltage is the same at both ends of the choke, then it's not doing anything for you. You could also measure the AC voltage from end to end on the choke. If this is nearly zero, the choke i...