CapnKen
11 posts
Feb 13, 2012
7:45 PM
|
Last night I went to a Blues Sociaty Jam and I took my old 67 Valco. I really wanted to hear another player through my amp. After I played 4 songs another harp player got up and was using my amp and mic. It lasted 1 song and then just shut down. I was really embarrased because the guy is really one of the best players in our area and he had to finish up through the pa. I put it in the shop today.
I told the tech to go through it and call me with his suggestions.
My question Is, what, other than fix whats broken should I have the amp tech do to set this amp up for harp?
|
bluemoose
681 posts
Feb 13, 2012
8:00 PM
|
Make sure it isn't the mic cable. Are you using a green bullet with a built in cable? The ground sheathing on the cable often wears out at the shell end, breaks and the mic fails.
----------
MBH Webbrain - a GUI guide to Adam's Youtube vids
FerretCat Webbrain - Jason Ricci's vids (by hair colour!)
|
CapnKen
12 posts
Feb 13, 2012
8:40 PM
|
No, I know it wasnt the mic,the light on the amp went out. Im hoping it's something simple, but the amp needed to be gone thru by a tech anyway.
I've had mic problems, like the screw on 1/4" adapter and cable problems but this was the amp just turning off.
|
5F6H
1070 posts
Feb 14, 2012
1:26 AM
|
If its never been serviced the "electrolytic" power supply caps & cathode bypass caps should be changed.
(The amp might have a multi-section cap "can", if so I'd leave it there, but disconnect it and replace each section with a discrete cap of good quality & voltage rating, B+ & screen supply caps ground to the main filter cap ground, where the old can grounds. Phase inverter & preamp filters ground to the input jack ground. Can caps are not good for hum/noise & it's difficult to find quality replacements...Valco ordered a lot of caps so the supplier back in the day made them to spec.)
This does not mean "change every cap in the amp", the majority of coupling & tone caps will be fine and only ones that show signs of leakage should go.
Fit new power tubes. Rectifier tube (if it has one) should be fine, assuming that is not what failed, rectifiers are usually "go/no go". Preamp tubes that are not noisy microphonic & still sound good can stay too.
If the fuse blew, that's because something drew too much current, like a failed electrolytic cap, or a power tube short, you don't want to replace just the broken part, only for an original part of the same age to blow next week! ;-)
Don't trust the light going out, by itself, as a sign of anything else being wrong, about a quarter of tweed Fenders have intermittent/non functioning pilot lights! Splash out on a new bulb.
If the amp does not have any "screen grid" resistors it's a good idea to add them, they give the power tubes an easier life. 470ohms minmum for 6V6 & 6L6, 4W rating, 1000ohms will work fine too.
----------
www.myspace.com/markburness
|
CapnKen
14 posts
Feb 14, 2012
5:30 AM
|
@5f6h- thanks for that info, thats exactly what I needed to know.
I want to get this all done at once because the last time I put an amp in the shop (Lonewolf mods on Valve Jr.) they took for ever to get it back to me, it wasn't Randy it was local.
How important is it to have a 3 prong power cord installed?
|
5F6H
1071 posts
Feb 14, 2012
6:33 AM
|
"How important is it to have a 3 prong power cord installed?"
Depends...how much do you like a hundred volts or so in the face? ;-) It's very unlikely to do you serious harm, but can seriously screw up your rhythm & best avoided all the same, especially if you sing and will be touching earthed equipment like PA mics, or likely to touch water pipes etc. in your rehearsal space. So, yes, fit a 3 prong cord.
----------
www.myspace.com/markburness
|
Littoral
487 posts
Feb 14, 2012
7:49 AM
|
5F6H: "...a hundred volts or so in the face...can seriously screw up your rhythm & best avoided"
Classic
|
NiteCrawler .
165 posts
Feb 14, 2012
8:17 AM
|
They don,t call those older 2 prong tube amps Widow Makers for nothing.For what its worth its really not a big expense considering the possible outcome,Git Er Done.
|
CapnKen
16 posts
Feb 14, 2012
8:17 AM
|
5F6H...HAHAHA ! I've got to admit I've never had a hundred volts to the face but, I tend to think I wouldn't like it much.
Thank you for your participation in todays episode of "Ask a stupid question, get a hell of an answer"
----------
http://www.reverbnation.com/#!/mudflapnicholsandthetwistedspokes
|
bharper
147 posts
Feb 14, 2012
8:52 AM
|
It was probably a power tube that popped. It happens. Did you see a flash of light from the back of the amp? It's a good idea to carry spare fuses and at least one power tube. (And a small flashlight.) You can quickly fix it during a break.
|
CapnKen
17 posts
Feb 14, 2012
1:39 PM
|
@bharper--no I didn't see anything, I wasnt around my amp at the time, another guy was play it. I agree, when I first got the amp I took spare tubes, but I quit after a while. Live and learn as they say.
----------
http://www.reverbnation.com/#!/mudflapnicholsandthetwistedspokes
|
