AMPEG SVT-CL rewiring for 220V and other issues

[MerlynMetal]

Hi,

A friend of mine bought a brand new SVT CL from abroad (UK). It's labeled for 240V operation but mains line voltage here is 220V. Is it possible to rewire the amp for 220V operation?
I collected some schematics from the net and it looks like the power transformer has two primary windings with 100 and 120V taps but voltage rewiring tables don't show a 220V option, only 230 and 240V.
Also the amp has couple of more issues. It worked for 20 mins and switched itself off. Now upon switching the Power on the fault LED starts blinking immediately. Also noticed that the fan isn't working.
Any help and advice would be greatly appreciated.
I'm sorry if I posted in the wrong area it's my first post here.

[BogeyBass]

I would call Ampeg and ask about the power transformer issues. Seems like 230 would be your only option, and if that does not work your out of luck....depending on ratio 10 volts of difference on one side can equal a big difference on the other side of the transformer.

If its not wired for 230 how did you operate it? The blinking light most likely means a bias problem and on a SVT is most likely a Bad power tube or more than one bad power tube.

They will need to be replaced with all new tubes and the amp will need to be biased. I hope you didnt fry the thing by running it on the wrong voltage...and if you did a tech should check and see if the bad tubes might have took out a few screen resistors.

Not to sound negative...get rid of it...sell it.....if its new its under warranty trade it in...if you ran that thing on the wrong voltage you might have damaged it and that will most likely void the warranty ...and if you plan on seeing your money i would leave that part out.

[aledeville]

Is 10V really a big issue? I remember the time when we had 220V (europe) and one day for whatever reason they raised it to 230V and not one single electric appliance had any problem.
But maybe a tech guy could answer properly.

[rodl2005]

AFAIK the 230 tap would be fine - I aint a tech tho. But when we swapped My SVTII from 110v to 240v I remember my tech saying + or - 10v was OK..... HOW 'OK' I don't know.

Send a 'PM' to TB member 'Jerrold Tiers' -he used to work at SLM making Ampeg tube amps & Should be able to help. He helped me re my 110v -> 240v swap

[BogeyBass]

Well thats good news then if 10 volts is not a big deal
then you just have bad output tubes.

Replace bad tubes and Bias and you will be running again.

[rodl2005]

I DID say I wasn't SURE!!!!!!! PLEASE - don't take MY word for it!!!

Ask Jerrold!! He's very knowledgeable re these Ampegs & helpful.

[MerlynMetal]

Thanks for the feedback!

If its not wired for 230 how did you operate it?

It's wired for 240V (that's what the label says) and it worked for 20 mins and then switched itself off.
Now it wouldn't go in standby mode because the LED starts blinking immediately after Power button is turned on.

Well thats good news then if 10 volts is not a big deal
then you just have bad output tubes.

How the amps can detect bad tubes or bias bias if no high voltage is present (unless maybe there is and open cathode resistor or something)?

I would call Ampeg and ask about the power transformer issues. Seems like 230 would be your only option, and if that does not work your out of luck....depending on ratio 10 volts of difference on one side can equal a big difference on the other side of the transformer.

I intended to do so but decided to ask here first. I sent them an email but no answer so far.
I was wondering if the 20V difference in the primary is messing up the fault circuit readings that's why I wanted to rewire the thing first.

[Jerrold Tiers]

It refuses to go OUT of standby if there is a problem, meaning it switches INTO "go" mode, and then activates an internal relay if there is a problem. Basically it "tries" the high voltage, and if a problem is sensed, turns it back off.

Concur that probably there is a bad tube, possible bad protection circuit..

As for the voltage..... While there actually IS a setting for 230V on most units, I wouldn't bother, really. The difference is about 4%, while regular mains voltage can vary at least 10% in many places and be within spec.

For 240, the operating range is nominally from 216V to 264V. You can generally go lower than that, but higher is more likely to cause trouble.

We at one time actually made SVT units that were set up for just 115 and 230V, and exported them everywhere.

[MerlynMetal]

Thanks for your answer.
From what I see in the schematics (and if I understand correctly) if fault circuit is OK it will generate a delay after which the relay allowing the high voltage transformer operation will be turned on which enables the Standby switch. THEN fault circuit will sense if high voltage and tubes' current are present. If either of them is problematic it will switch off and the LED will start blinking. In my situation the LED is blinking right after POWER is turned on which I suppose indicates bad fault circuit because neither high voltage nor tube current are present to sense at that time (unless the fault circuit can sense other problems as well).

[jetofuj]

Jerrold, do you remember if older SVT II (non pro) also has universal transformer that can be switched to 220-240V?

Cheers!

[dincz]

Wkipedia: "All of Europe and most of South America, Africa and Asia, as well as Australia and New Zealand use a supply that is within 10% of 230 V"

So the 230V mains supply can vary within the range 207V to 253V. The 220V standard where you are was raised to 230V some years back - unless you're somewhere really off the beaten track.

[jetofuj]

I know, ha, ha...

It was just a question if older SVT II has export transformer or not

[Jerrold Tiers]

I answered the PM, but for the II, it depends on whether it's an export model or not, both were made. The decision to make just universal units was later, and I don't know if any SVTIIs were included, but I don't think so.