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Ampeg svt3pro - has my nightmare begun?

Andysalt01

Andysalt01

Apr 21, 2006
185
192
United Kingdom
gevaudan.bandcamp.com
#1
Hello! This is my first post and unfortunately its a cry for help. :help: I've run searches and read through threads for about 3-4 hours now but need some input if possible.

Basically, I bought a second hand Ampeg svt3pro (I really loved the tone), tested it prior to buying and it ran fine. I got it home, plugged it into the mains directly to check it was still in order (although no cab connected - which i understand is ok as the power amp is solid state) and it was fine, peak flashing as the gain was adjusted. Anyway a week later - i was bored, popped it on again, and it died. :crying: Checked the kettle lead and that was dead. I took it down to the techie at the Bass Centre who gave the amp a once over, replaced a couple of transistors that were burnt out and some tubes and i ran it for 20 mins or so in the shop and bought a new kettle lead. Lovely.....didnt put it on again until i received the cab.

Received my cab today - brand new :hyper: - plugged everything in securely checked and double checked, all hooked up switched it on :bassist: .........the same thing happened - the amp came on the fan started up, and after about three seconds the amp died. The kettle lead is dead again, but i dont have a way to check the amp. A few questions then from this - firstly, any ideas? could it be a repeating problem? does it sound like a fault with the amp or the power supply? The second time i had it plugged in via an extension lead.

Any assistance would be welcomed, or previous similar experiences I'm really not a tech head and trying to learn as much and as quickly as i can. I'll be taking it back for a recheck i think. Thanks, and someone please rock on for me! :bawl:
 
#3
I had a problem with my SVT III Pro fan. Got it replaced but that was two years ago and it runs good. Sounds like one of those "the symptom was fixed but not the cause of the problem". Keep at it. It's a good amp.

Where's Jerrold?
 
#5
Oh yeah, sorry 'kettle lead' probably isnt a universal term - its basically an a female 3 pin IEC plug on a standard mains cable for a 3 pin UK mains plug, used on a lot of electrical things in the UK - computers, amps etc. hope this is useful!

It had crossed my mind about the previous owner - but i have no come back unfortunately - have mailed him but no response.

I do really want to stick with it its just frustrating....I'll have a look into the fan or similar ideas, thanks man.
 
#6
Do you know any history on the unit?

It isn't THAT complex to fix, although it would help the tech to have a schematic etc.........

There is a whole universe of possible problems.

You are in the UK. Therefore your "kettle lead" ( mains power cord) is fused...

The simplest possible one is that the fuse in the cord is wrong sized, and it blew from the in-rush of current as the unit was turned on. it is possible that the power supply got charged up enough to run the fan before the fuse blew, and then of course discharged and the unit was then "dead".

If your tech turned up the power voltage with some sort of variable transformer, he wouldn't have had the "in-rush"......

It needs a cord with at least a "T5A" fuse, which is what should be in the rear panel fuse holder on the amp rear panel for 230/240V.

If the fuse in the cord is opening before the fuse in the unit, the cord & fuse is too small (OR the fuse in the unit is too big).

That would be a simple fix...... if that is what's wrong.

Otherwise, lots of possible stuff................ including bad bias setting... The bias setting is a bit more important on those, because of the way the power amp is made. Get it too high, though, and it is like a short across the power supply.
 
#7
Thanks Jerrold - you've filled me with confidence! :smug: and I've got that excited feeling back in my stomach rather than the sinking one of despair!

Looking at the power leads i have - they state "10A 240v" - so if my understanding of fuses is right, this is probably the problem :confused:

Is it likely to have caused any damage to the amp, or fused at the plug and saved it from harm? Sorry for my ignorance - like i say, i'm still trying to learn even some of the basics....

Really appreciate everyones help on this!!! thanks
 
#8
Andysalt01 said:
Looking at the power leads i have - they state "10A 240v" - so if my understanding of fuses is right, this is probably the problem :confused:

Is it likely to have caused any damage to the amp, or fused at the plug and saved it from harm? Sorry for my ignorance - like i say, i'm still trying to learn even some of the basics....
Click to expand...

The 10A is OK for your cable. But clearly a 10A fuse that blows before the back-panel 5A fuse is not quite right...... even if there were an internal problem, the 5A fuse should blow first.

So if it is a fuse problem, one of two things is probably the issue.

Either the fuse in the unit back panel fuse holder is wrong (too large) or the "kettle lead" fuse is a fast-blow type.

You need a slow-blowing type fuse, for which the IEC designation is a "T" followed by the amp rating, like "T5A", which is what should be in the rear panel fuse holder.

If there isn't anything already wrong inside, blowing the line fuse due to "in-rush" won't hurt anything.

Check with the tech (or whoever) about that fuse in the "kettle lead". A fuse that is NOT a "T" type may blow almost instantly.

(I assume that "kettle lead" comes from the old-type plug-in power leads on coffepots, cooker kettles etc.... they had a fat plug at the end similar to a new-style standard plug-in cord.?????)
 
#9
Also how old is the amp? If I understand correctly, Ampegs are under warranty for 5 years and the warranty is transferable, so if the amp is less than 5 years old it would make sense to have an authorized Ampeg service tech keep after it until it's fixed. You already know how good these amps sound. Of course even if it's out of warranty, I personally would only trust it to an authorized Ampeg repair tech unless it was a special circumstance where you knew the tech or he came very highly recommended. Somebody please correct me if I am misunderstanding the warranty.
 

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