caps

[jtourangeau]

i am a low voltage tech looking maybe to make the jump to high-volt tech.ok....im a cable guy.... any hoo. im am a guitar player and fancy vintage equip for reasons of piont to piont hand wiring and tonal qualities.i currently have an amp i'm trying to "restore"/ make work.ive taken it apart and noticed blisters on the face of one "cap" and the main tranformer is leaking oil.the amp in question is a music man rd 100 i belive to be late 70's early 80's.im pretty sure the cap could use replacement.not sure on the xformer.the amp "works" but sounds like crap under a good "load".if i replace the cap,how do i drain the bad one.i have a feeling there is energy stored in it but am not dumb enough to put my toung on it to find out how much.i do know how to use a volt ohm meter to find out how much v/a is in it .i am not sure how to properly drain it.definantly dont want to use a rubber glove and scewdriver,as i would like to use/fix this thing....yes i found you with google,yes i did read the "newb" page.so....i did read 10 peoples version of OHMs law.... i understood it to be E=I/R. but im no pro. thanks for any help....im sure ill take a good beating judging by the noob page. jt

 

[KeepItSimpleStupid]

Kinda funny. Welcome. I haven't really seen fluid filled transformers except the big ones 100 kV or the ones used for power distrbution. If the transformer's "fluid" is har and usually yellow, it's a varnish used to keep the core tight.

Your right. No tounge. That's the way my kid friends of decades ago used to test 9V batteries. MOST, I said most, caps will have bleeder resistors if the designer expected them to hold a charge. Caps rated in the kV range will develop a charge by looking at them. You have to store them with keepers. Consumer stuff is not going to be that bad so don't mind me scaring you.

A voltmeter on the range of the rating, usually expressed in VDC or WVDC in old times) of the cap across the cap will tell you if it's OK to touch. The big capsinthe 10's or 100's of UF are usually filters and are good to check to ground to see if you can now use your fingers.

Cap's can be discharged with a resistor. Estimate the voltage and pick a resistor and make sure I^R is within the rating of the resistor. Within 5*R*C, the voltage should be gone. ex. 5 * 1e-6 (for 1 uf) * 1,000,000 ohms, or within 5 seconds the charge will be essentially gone, but wouldn't hurt to check.

There are sites better to help you with replacement parts for restoring tube electronics such as **broken link removed**.

Feel better?

 

[jtourangeau]

quickie

thats truly awesome,within 5 min i got a reply.ill check your link and come bk here if i need emergency responce. ,,,no beatings? i almost feel cheated. howbout grammar or what do you call the commas and periods and stuff???11#4%%6 much thanks jt

 

[KeepItSimpleStupid]

And when you want to try to modify stuff and get rid of the hum, then there is this site: New Low-Voltage and High-Voltage Regulator Kits that I found recently. Use John Broskie's Guide to Tube Circuit Analysis & Design as the initial URL.

Now this will confuse you: **broken link removed**

Note that there are different capacitor types.