Metro JTM45 PT B+ Voltage

out of focus · Post by **out of focus** » Sat Aug 15, 2009 12:04 am

My Metroamp JTM45 Power transformer is only putting out around 370V B+.. Is that typical of the metro PT.. I built it in Nov. 2007 and I seem to remember that it was around 410-415V. before .. Would the AC wall voltage being around 117V cause this ? I think the AC was a little higher at my old house.. Still sounds sweet anyway, just not as loud and punchy..

Structo · Post by **Structo** » Sat Aug 15, 2009 1:56 pm

You really only have 117v from the wall?

Strange, the house current many years ago was 115v but it was moved to a 120v standard for some reason.

But yes a 3v change could translate to lower secondary voltages.

I don't think it would 30-40 volts though.

out of focus · Post by **out of focus** » Sat Aug 15, 2009 4:25 pm

Yeah.. Houston's power supply is a little shoddy.. I even replaced the the rectifier tube with a NOS GE from TubeTramp thinking that it may be the cheap chinese one I had before..

Drifting · Post by **Drifting** » Sun Aug 16, 2009 12:46 am

30-40v difference seems drastic.

I've read of a few recent builds being a little under 400, including my own which is about 395, but I've never read of a 45 with that low of a B+.

Mars Hall · Post by **Mars Hall** » Sun Aug 23, 2009 4:48 pm

out of focus wrote:My Metroamp JTM45 Power transformer is only putting out around 370V B+.. Is that typical of the metro PT.. I built it in Nov. 2007 and I seem to remember that it was around 410-415V. before .. Would the AC wall voltage being around 117V cause this ? I think the AC was a little higher at my old house.. Still sounds sweet anyway, just not as loud and punchy..

I had a similar problem with low plate voltage. After replacing the choke in my JTM45ri, I figured out I had it wired wrong. Here's the thread.

http://forum.metroamp.com/viewtopic.php?f=15&t=27258" onclick="window.open(this.href);return false;

After first replacing the choke plate voltages looked normal, not until later did I notice the large drop.

out of focus · Post by **out of focus** » Sun Aug 23, 2009 10:20 pm

Glad that you have figured out what was wrong.. I am going to check that out on mine tomorrow..

Mars Hall · Post by **Mars Hall** » Mon Aug 24, 2009 6:13 am

I assume you have the 3H choke, which would explain why you don't have as big of a voltage drop as mine did, if you have the same problem.

out of focus · Post by **out of focus** » Mon Aug 24, 2009 3:10 pm

Well.. Mine is hooked up the right way

But I am starting to wonder if the filter cap may be bad because I noticed the other day while I was playing the amp that the Indicator light blinks on and off at a very high speed like the ripple of electricity.. Anyone ever had that problem or noticed that on their amp ?

Structo · Post by **Structo** » Tue Aug 25, 2009 2:40 pm

Is it a neon pilot light?

out of focus · Post by **out of focus** » Tue Aug 25, 2009 2:51 pm

It is the Orange 120v. lamp that comes with the kit

uiovbged332 · Post by **uiovbged332** » Wed Jul 06, 2022 3:57 pm

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Metro JTM45 PT B+ Voltage

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