Egnater Tourmaster Amp Repair Help

[ks_cuervo]

I'm hoping I could get some help sourcing finding/source some parts. I'm repairing an Egnatoer Tourmaster 4212 Guitar Amp that's blows a fuse on powerup. I'm starting with replacing the caps on the power board. I've been able to find a chinese version of the schematic (see attached) that matches my component board values and identifications, but actually finding replacement caps has been a struggle. Hopefully someone can help me out. The large caps have a pretty distinct marking but I'm not sure exactly what manufacture it is. See pictures for reference.

[Muxr]

Not familiar with that capacitor brand.

In either case, I did a search on Digikey and found some quality Nichicon caps which match (or exceed) the specs: https://www.digikey.com/en/products/detail/nichicon/LKX2G331MESA50/2541238

[themadhippy]

but I'm not sure exactly what manufacture it is.

dont really matter the make,the important bits  are the value of  330uf,  rated for at least 300v,and they will physically fit,the pin pitch being the most critical.

[ks_cuervo]

Thanks for the feedback. I figured the specific manufacture wasn't too important, but also was looking for thru hole 330uf 300v with dimensions around near 25mm diameter and 41mm height, but hadn't come up with anything. Expanding that to any rating above 300v and changing the package type to be radial can/snap in brings lots more options.

Is there any guidance on how to determine the best for my use case? Just lowest cost or are there other variables I need to be considering?

[Muxr]

Is there any guidance on how to determine the best for my use case? Just lowest cost or are there other variables I need to be considering?

Make sure you match, capacitance (330uF), you can exceed the voltage rating (300V+), and you can also exceed the temperature rating (2000 hours @105) if you want.

These appear to be high voltage filtering caps. So low ESR would be probably a nice bonus, but not critical.

I personally stick to proven good brands like Nichicon, Rubycon, Kemet.. And make sure you got the dimensions/form factor you need.

That's about it.

[MathWizard]

So what kind of PSU's are in AMPs these days ? If you're on 120VAC which rectifies to about 170VDC, but that cap is rated 300V, is there a setup up transformer? Or have they gone with SMPS ? And if so,  I wonder how much noise from switching is in the audio range, before filtering ?

OK I missed the schematic, it has a step up transformer.

I guess some amps still use high voltage tubes too.

[ks_cuervo]

This amp is a few years old now. I believe it was purchased in 2010 or near then (not that SMPS weren't around), but tubes still rule the world in "high end" guitar amps. The original step up transformer was a toroidal that shorted internally and was replaced byhttps://www.mercurymagnetics.com/wp-content/uploads/shop/specsheets/EG-TOURMASTER-P.pdf] [url]https://www.mercurymagnetics.com/wp-content/uploads/shop/specsheets/EG-TOURMASTER-P.pdf[/url]. After the replacement the amp has worked for awhile, but then started blowing a the 500mA Slow blow fuse, F5 from the schematic, which has spurred this cap replacement effort.

[MathWizard]

Ok so this is just the PSU section, and the B1 - B6 type stuff are just the HV rails right ? IDK how much tube currents change over the years, or their circuits, but what about those large wattage resistors R178 -181, I wonder if their value has changed much.

How close was the replacement transformer ? Do you know any before and after voltages ?


I have a 10W practice amp, I recently too it apart to learn a bit more about op-amp circuits, and there's only 1 dual op-amp in there, for the distortion circuit. So I've been looking at distortion pedal schematics, some day soon I'll try one, surely it will be better.

I don't need much volume, and I could add another speaker if I wanted to use a bigger transformer.

[ks_cuervo]

Correct that this is jut the PSU section of the schematic and B1-B6 are the HV rails. I have another sheet covering the tube channels. I haven't measured R178-181 specifically, but can do that this evening.

I don't have any before and measurements for the transformer, but I should take and document those for the Mercury.

[Vicus]

If any of the 300V capacitor is short (C126, C127, C130, C131) so the fuse F2 and F4 have to blow.

[ks_cuervo]

Yes, I understand this and actually expect the culprit to be one of the 450V caps (C136-139 or C150).

The initial question was regarding distinguishing cap brand based off the marking. I can tell the 300 and 450V caps are the same brand, but since I'm replacing some, I figured I'd do the whole board to hopefully save having to open it again in the future.

[DavidAlfa]

Start by searching for shorts in the power transistors, rectifier... electrolytics can short but it's very rare.

In any case you don't need audiofool parts, any 300V+ rated electrolytics will work,.