filter cap substitution

[selloutrr]

I'm doing a cap job on an amp. it has a couple 40MFD-40MFD@450v caps. My options are...

1.) replace with an F&T 33MFD-33MFD@500v which fits in the OEM bracket
2.) replace with a 50MFD-50MFD@500v can cap which requires a mounting bracket and some fabrication.

Thoughts? Pro's / Con's

[dehughes]

I vote Option 1, as I'm nearly always for lower filtering and less fabrication.

[Structo]

Does the amp work right now and if it does how do you like the way it sounds?

Measure the caps to see where they are at right now.

20% tolerance of 40 is 32 or 48.

So either way you are within tolerances.

Now it's just up to the ears.

[JamesHealey]

33 40 is close enough with filter cans. Tolerances are big on these.

[Bob-I]

I'm doing a cap job on an amp. it has a couple 40MFD-40MFD@450v caps. My options are...

1.) replace with an F&T 33MFD-33MFD@500v which fits in the OEM bracket
2.) replace with a 50MFD-50MFD@500v can cap which requires a mounting bracket and some fabrication.

Thoughts? Pro's / Con's

Kinda matters what amp, tube or SS rectification?

[selloutrr]

it's Traynor YGL-Mark 3 head, totally dead right now, all the electrolytics are shot and few resistors. The tubes are burned to under 20%.

The chassis is pretty good.
The transformers test good.
Mustard caps are good.

The same amp used for Radiohead's Creep. It should sound like a fender twin when it's working.

I like the 33MFD Idea too.

Thank you, I'll post some pics when I get motivated enough to fix it.

The combo's came with JBL K-120's 8ohm. wired for 4ohms.

I picked up an empty Traynor 4x12 I'd like to load with 16ohm K-120's.

[daydreamer]

I see you have a Traynor there, would you mind letting me know if these filter caps you are talking about are the ones "smoothing the power" that the Trainwreck pages talk about? I'm trying to workout how to reduce hum coming from my Traynor Darkhorse 15 watt. It is running on 110v/ 50 hz power ATM but it is designed for 60 hz (I assume there is something designed to deal with the different frequencies) am I on the right track thinking there is something that could help like changing the power filter caps?
thanks

[Structo]

I don't think any amp does anything different to deal with the different AC frequencies.

A 60 Hz amp should work fine at 50 Hz as long as the voltage is correct for the power transformer.

[selloutrr]

which TW pages are you referencing?

Yes the large electrolytic capacitors help smooth the power.

If you have excessive noise and your electrolytic caps are original they are pushing 30+ years. It's time to replace them.

[daydreamer]

Sorry, I didn't see the question selloutrr, the TW pages I was reading are here:

http://angela.com/thetrainwreckpages.aspx

Thanks for the help, I will go back to the mains AC and start there. Then I think I will have a go at the electrolytic caps. It wouldn't do to have equipment in my studio I haven't pull apart...

[selloutrr]

its really strange you are having ac hum issues with a new amp.

are you runnin it on a power outlet that shares with lights or something like a dishwasher?

some of the new production traynor have been reported to have issues with pcb traces.

check the bias,
spray some caig deoxit cleaner on the pins of the tubes and reseat them a few times.
try swapping out the preamp tubes with know good ones.

make sure everything is tight to the chassis esp the ground

[daydreamer]

I'll do all of the suggested checks, and as far as lights and appliances- nothing on that circuit that would hum like that, the fridge is on it but it runs intermittently (as they do).

I'll let you know if the inspection/ tighten up/ re seat/ ground check, tube swap etc works,
like you said, if it is new and meant to be filtering the power, then why would it pick up so much hum? even from a noisy transformer (if I understand correctly), it should be isolating the amplified audio signal from the mains power, not amplifying buzz.

A PCB trace? what would that look like? or does it mean I'm screwed! i starting to get impression my first project will be to rebuild this amp in the point to point style- just gut it, use the chassis and components and put it down as the world most expensive kit amp! !!