The Amp Garage

The output transformer is quite an old version. It has a 5.5K primary from memory and it is quite loud. I remember RJ’s was quite full on. I thought it was in the vein of Richie Hall’s amp. https://youtu.be/HHiJrufUbF0?feature=shared https://ampgarage.com/forum/viewtopic.php?t=30033 https://cdn.shop...

Stevem wrote: ↑Fri Apr 19, 2024 10:01 am Yes they are not at the bottom of the ladder any more.

What makes you believe they are a good brand to use again?

What is on the bottom of the ladder these days?

I think F&T is my cap of preference, though if Nichicon had a product I would use that.

This problem was specific to Fender amps manufactured over some range of dates, and limited to IC electrolytics sold to Fender, IIRC. Great to hear from you as always Martin. I appreciate your input. I must admit that I don’t know if the bad IC brand caps were limited to Fender. Perhaps if there wa...

I think that will be your biggest challenge finding the right parts. The parts of greatest concern are the transformers. I would build it on a Garolite board, phenolic boards can be conductive and you don’t need that. https://modulusamplification.com/wrocket-top-boost-30watt---4-x-el84-head-kit-3229...

In the past I’ve seen quite a few fender amps with IC branded capacitors which are leaking, I dare say quite a techs made a good living replacing capacitors from Fender amps.

Have IC caps turned a corner and become reliable or do they still leak?

I probably would look for something like this Hammond output transformer. https://www.hammfg.com/part/1628SEA If you disagree that’s fine, but I would like to know why. It is touted as a Hi Fi transformer, but I don’t like Class A amp with rubbish bass response generally. From my experience this tra...

Measure the leakage at rated DCV. Measure the ESR. Measure the capacitance. Look for deformities. Fairly simple, but it takes time. It can be done by lifting one leg with care, and can be done using the amp's power supply when you have a variac and use a series resistor for current sensing. Right, ...

]The Two Stroke seems a strange amp to me. The tone control on these amps is nice but it does mean the amp loses signal so it doesn’t have the same break up as a Champ. I don’t know why the second 1.5K cathode resistor wasn’t bypassed by a 5uF to 22uF cap for extra gain and a 47 ohm tail resistor pu...

It’s not a question I thought I would be asking but here I am. I use the ESR-70 to determine the condition of the filter caps. I have mentioned this online and been roundly told this tester won’t determine if the cap is leaky and I should simply replace the caps. I tend to think if the cap was leaky...

That master volume mod doesn't actually help, I did some tests on this a few years ago with a spectrum analyser and found it made no difference. But YMMV. Dave Friedman puts a 500pF cap across the cathode follower 100K, lowers the first coupling cap to .0022uF, adds a 22uF to the final stage cathod...

Mystery double post.

bepone wrote: ↑Sat Apr 13, 2024 1:50 pm Speaker is v30? Change the speaker?
Some other guitar problem?

I used a EVH MIM guitar, and I also used my Strat. The box is a Fender Bassman box with Kendrick Blackframe speakers in it. I have previously used the box with a 1959 and it sounded fine. The speakers aren’t overly bright.

I plugged into my friends 2203 and it sounded dreadful. It was overly compressed and the treble is raspy. The compression was due to the 100K cathode follower resistor measuring 880K. I replaced it and the amp sounded much better. The amp still has raspiness which goes away when I turn the volume up...

Thanks for your advice I appreciate that.

I’m working on a JCM-800 and I find that the bias voltage ranges from -58VDc to -42VDC. I have tried the EL-34’s that the amp came in with and a new set. I find with a new Marshall branded set if EL-34’s the maximum they will pull is 27mA. The bias circuit is incredibly simple. A diode, two resistor...