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Author Topic: My JVM died  (Read 9799 times)

robert

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My JVM died
« on: January 13, 2014, 09:32:10 PM »
A fuse blew. FS3 is the name of the fuse. The V1 preamp lights up, but all other tubes are dark and cold.

See http://jvmforum.com/phpBB3/viewtopic.php?f=7&t=1321&hilit=fuses for a picture of these fuses, FS3 and FS4.

The remedy is apparently to solder wire there instead, since those fuses are not necessary according to Marshall.

I'm still scared of doing that, so I just tried with 2 new fuses and no difference I'm afraid... what to do? Not sure there will be a qualified amp tech around here.

« Last Edit: January 13, 2014, 09:50:38 PM by robert »

zagatron1

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Re: My JVM died
« Reply #1 on: January 13, 2014, 11:48:59 PM »
Do not solder "a" wire on each (FS3 & FS4)! If you look closely, it appears the circuit (heater) was split by-passed. In essence the equivalent 4 wires were being used also. Oh, I found something!
Here's what the Marshall folk say.........

COMPANY STATEMENT
(Reference JVM410 Heater fuse removal)
Units affected
Products produced before or during manufacturing week 24 of 2007 (serial number on product
states the week of manufacture number ex.: M-2007-24-1234-1).
Affected PCB s will be marked as PCBP-00129-01 / 02 / 03 / 04

Action to take
1. Remove fuses and fuse holders from location FS3 & FS4 on PCB and replace with 2 wire
links per fuse soldered in positions shown below using WIRE-20045. 21swg Tinned link
preformed to 26.5mm long and 5mm high.
2.Cover fuse ratings of FS3 & FS4 (T10A) marked on PCB silk screen with TIPP-EX.

I believe you already have a pic from that jvm forum link to refer to.
« Last Edit: January 14, 2014, 12:02:06 AM by zagatron1 »

Vladan

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Re: My JVM died
« Reply #2 on: January 14, 2014, 09:50:30 AM »
Robert, I'm afraid you have bigger problem. If it was only blown fuse(s), new one(s) would make the amp work.

Fuse is just a straight wire of certain thickness, placed in a glass tube. So, soldering heavy gauged straight wire is not a remedy for blown fuse, but a remedy for occurrence(s) of blown fuse(s) i.e. with thick piece of iron, e.g. an iron nail, there are no fuses to be blown.

If that's a photo of your own amp's PCB, it's noticeable one fuse slot got the heat transferred to PCB and burned it, so it got that burnt black tint. If it turns out it's not only fuse, you'll have to look there and onwards, for blown elements, cut tracks  and cold solders.
« Last Edit: January 14, 2014, 09:54:27 AM by Vladan »

robert

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Re: My JVM died
« Reply #3 on: January 14, 2014, 11:15:14 AM »
Ok, not sure if I should do this myself or not. Is it hard to unsolder and solder on a board? I have never done that. I have a 20w/40w soldering iron. Tell me all I need to know - I don't want to wreck anything.

zagatron1

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Re: My JVM died
« Reply #4 on: January 14, 2014, 11:35:45 AM »
Ok, not sure if I should do this myself or not. Is it hard to unsolder and solder on a board? I have never done that. I have a 20w/40w soldering iron. Tell me all I need to know - I don't want to wreck anything.

I do that kind of stuff all the time. The soldering iron you got is okay but if you feel uneasy taking that challenge, don't attempt it. Too easy to burn a trace if you're not careful.

robert

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Re: My JVM died
« Reply #5 on: January 14, 2014, 11:41:28 AM »
What the solution if you burn a trace?

zagatron1

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Re: My JVM died
« Reply #6 on: January 14, 2014, 11:53:46 AM »
What the solution if you burn a trace?

Trust me, you don't wanna know. It'll be one of those "What do I do now :-\" moments. I, however do keep a couple of these handy - http://www.mcmelectronics.com/product/200-175  for such occasion.

robert

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Re: My JVM died
« Reply #7 on: January 14, 2014, 07:56:32 PM »
I think I will try and find a local repair electronics guy to do it for me...

zagatron1

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Re: My JVM died
« Reply #8 on: January 24, 2014, 12:08:26 PM »
Let me know how it went. Curious you know.

robert

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Re: My JVM died
« Reply #9 on: January 25, 2014, 06:00:49 AM »
I'll take it to a repair guy someday soon. I'd like to get it to work again... it's a cool amp.

zagatron1

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Re: My JVM died
« Reply #10 on: January 25, 2014, 02:41:01 PM »
I'll take it to a repair guy someday soon. I'd like to get it to work again... it's a cool amp.

If I resided near you, I'd offer my services.

robert

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Re: My JVM died
« Reply #11 on: January 27, 2014, 10:16:37 AM »
Thanks a lot Zag!

DetroitBlues

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Re: My JVM died
« Reply #12 on: February 08, 2014, 10:28:01 AM »
I'd go the safe route Robert... Get it to a tech... Best chance for a full recovery.