epi valve sr

[moondog2u]

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new to site

« on: September 06, 2012, 03:39:33 pm »

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like it says new to site,
the other day i turned on amp and it started popping,
so turned off and checked cables, then turned back on
thats when all the smoke started and wou what a smell,
so i tore down my epiphone valve senoir,
first thing i noticed was a burn on pc board,
a ceramic resister and a cap, were burned,
i guess a cap it had brown paper all around it.
and snow in one of the 6v6 tubes
what im really looking to find out is
what parts i need to get to get this amp back running
maybe with a hand wired board and all new parts,
to add to the carcus of the old valve sr.
any and all help would be put to good use!
were are my manors?
hello from texas!
i did stop by guitar center in clear lake tx, sub of houston cross the freeway!
 and pick up a hotrod delux 400 bucks used w/ 1year!
so living room is good!
epi sr in laundry room but getting slack to chunk,
please help before made to!
thanks if just for taking the time to read!
john
moondog2u
 

[moondog2u]

i always said if anything ever happened to it i was going to totally rebuild!
well it did and here i am trying to figure out where to start!
i had 2 6v6 and 3 12ax7 in carcus chassie
does anyone know what would fit in it
and have a point to point
i cant throw old carcus away
eventhough i have never done an amp before
but gonna have to.
thanks
john
moondog2u
 

[HotBluePlates]

... a burn on pc board,
a ceramic resister and a cap, were burned,
...
and snow in one of the 6v6 tubes ...

The ceramic resistor you have a close-up of is definitely blown apart. See this pic for what it should look like. Additionally, the cap next to it has blown up.

The "snow" in the 6V6... Is that white stuff where the good 6V6 is silver? If so, that tube is broken, has lost its vacuum and will never be good again. Throw it in the trash and get a new 6V6.

I had trouble finding a schematic, but hopefully this one is legit (it was drawn up by someone other than Epiphone).

I *think* the resistor in question is R22 (please confirm this; I have trouble reading the part # by the resistor on your board). The blown up cap is probably C25 (please confirm).

If my guesses are right, the output tube was damaged (dropped, pins forcefully bent, glass cracked, etc.) and air leaked in. When you then applied power, the tube didn't work properly and sucked BIG current. The output tube cathode resistor and cap then burn and explode.

Get a 250Ω 10watt resistor and a 1uF 50v radial electrolytic cap (you can go up on the uF rating up to maybe 25-50uF, as availability dictates). It doesn't look like anything else is burned, but we hope you don't have damage to the power or output transformers. You could replace just these two parts and probably have a working amp.

If you are dead-set on a gut-n-rebuild, the original amp is much like a reverb-channel-only Deluxe Reverb, without tremolo and with modified parts values. You might do well to build the original Valve Senior circuit on a board that's easier to tweak/modify than a p.c. board. You could then get the amp working, and afterwards modify to suit your tastes.

[moondog2u]

looked and it is r22 on the resister
but the cap is blown and the board so burnt
will have to take your word on that!
is there any way to clean that board to be able to reuse
when it burned it stinched the whole living room,
thank you for your help sir!
john moondog2u

[HotBluePlates]

You'll need to unsolder the old parts from the board, then scrape away the carbon residue. Clean up that area afterwards with some isopropyl alcohol (not rubbing alcohol).

The alcohol may help remove the last traces of the carbon, but I haven't had good luck using it to remove the heavier deposits, which is why I recommended scraping first. Just work carefully with a razor or Xacto knife, and use the least pressure that gets the job done.

After cleaning the area, install the new parts and solder in place.

[moondog2u]

hay sir how you doing today!
i worked on it a bit today,
pulled card from amp and removed old parts,
went to electronics store
found cap but resister, could not find
talked with the parts fellow,
long story short: i got a 25w 270 ohms,
but i did find some isopropyl alcohol and got board cleaned up
so what do you think about that resistor,
10w 250 ohm stock
25w 270 ohm what i got
i did look fo 2 500 ohms 10w no luck
so do you think she will fly? or smoke?

[sluckey]

It ain't gonna smoke that resistor! You're good to go.

[jeff]

moondog2u could you please tell me if the power transformer is marked? What are the numbers on it.
I'm not sure but I heard that the same transformer used in the Valve junior was used in other epip amps.
If they did use the same transformer this would give me a better idea of what I can build with my VJ Xformer.
The Xformer I have is marked

A 06283770(seperate thin white sticker)
BLK  -  WHT  -  YEL  -  BLU  -  BRN
  0   - 100 V -  115V - 230V - 240V
YW PT-779-G-100/115/230/240V
12V -0 -12V     6.3-0        260V-0
BLU-BLK-BLU   ORG-ORG    RED-RED
              TC00273

Thanks
 Jeff

[moondog2u]

valve senior power xmf
white sticker on it, only markings!
XL76-14
DC94-512-01
I/P:AC 100V/115/230V/240V
COM BK/BLU/WHT/RED/BRN
O/P:AC 300V-0.225A RED-RED
AV 3.15VX2-5.0A ORG-YL-ORG

SMALL ONE
XL66 025
DC94-513-01
COM 4 8 16 OHM

HOPE THAT HELPS

[jeff]

Thanks. I appreciate it.
 Jeff

[Willabe]

Hey moondog2u, before you fire up that amp you should build 1 of these light bulb current limiters. It's easy to build and doesn't cost much.

It really is a must have must use tool for amp repair and new/tweaked builds. It can save your PT and more if you have a short in the amp somewhere.

Here's the link from sluckeys site with instructions;

http://home.comcast.net/~seluckey/amps/misc/Amp_Scrapbook.pdf


                    Brad      

[moondog2u]

thanks fot the test tools!
i hate to say it
but i did test, or should i say smoke tested
with no smoke! thank goodness!
set all my pots to 0, and put all the nobs on at 6 o'clock
then went to 9 o'clock on all pots had a friend strum my guitar
while i held power cord in hand looking at tubes,
i just had on work bench not in cab, put in cab.
i'm an electrician by trade, and dont clame to be an et or amp tec
i really dont understand the inter working of an amp,
but i have an epiphone valve jr, and i just ordered a mod kit for it, from bitmo
maybe i will learn a little bit about them,
thanks and i will be saving prints!
john moondog2u

[HotBluePlates]

Congrats!!

If you're an electrician, you'll figure the amp stuff out before long.

So this is one case where you could have replaced the obviously burned parts with no problem. Hopefully, you'd have noticed the one 6V6 didn't look right, or you'd have smoked the new parts. But good on ya for checking, as there's other ways for an amp to fail where the burned parts are the only thing to fail, but merely the symptom.