Update on this. I took it to a tech and he did some checks and yes it was the inrush current due to the bigger than required transformer.
Swapped the 500mA Fast-Blow to 500mA Slow-Blow and all is well.
Replacement Transformers
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Re: Replacement Transformers
Last edited by hywelg on Mon Aug 08, 2016 9:43 am, edited 1 time in total.
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martin manning
- Posts: 13404
- Joined: Sun Jul 06, 2008 12:43 am
- Location: 39°06' N 84°30' W
Re: Replacement Transformers
Good to hear it's solved.
Re: Replacement Transformers
It appears my fuses are right on the limit!
Since the previous post I've used the amp a couple of times and worked it hard at our Monday night jam. Behaved fine. Then I gave it 3 weeks off and its got lazy. Blew a fuse straight away. (I then used a different amp as I didn't take the spare fuses, I thought it was all good, grr!!) Took the amp home and powered it up, mains fuse blew straight away.
Put the light bulb limiter on it and it glows brightly for about a half a second then dims, as you'd expect. Tested each valve in turn to see if any particular one was drawing an excess, no, nothing out of the ordinary. Tried =C= in place of the TAD power valves. No change.
Took the light bulb out of circuit and the fuse holds up. So maybe I think the heaters are now warm, maybe they'll draw a little less?. Powered it up from cold this morning, no problem. What I didn't check yesterday was the mains voltage. Today its 241.5. I dont often see it much higher.
So I'm taking it to the jam session tonight and we'll see what happens.
It seems the 2A SloBlo mains fuse is right on the limit for 240v mains and the inrush current at power on. How high can I take this without creating a risk?
Since the previous post I've used the amp a couple of times and worked it hard at our Monday night jam. Behaved fine. Then I gave it 3 weeks off and its got lazy. Blew a fuse straight away. (I then used a different amp as I didn't take the spare fuses, I thought it was all good, grr!!) Took the amp home and powered it up, mains fuse blew straight away.
Put the light bulb limiter on it and it glows brightly for about a half a second then dims, as you'd expect. Tested each valve in turn to see if any particular one was drawing an excess, no, nothing out of the ordinary. Tried =C= in place of the TAD power valves. No change.
Took the light bulb out of circuit and the fuse holds up. So maybe I think the heaters are now warm, maybe they'll draw a little less?. Powered it up from cold this morning, no problem. What I didn't check yesterday was the mains voltage. Today its 241.5. I dont often see it much higher.
So I'm taking it to the jam session tonight and we'll see what happens.
It seems the 2A SloBlo mains fuse is right on the limit for 240v mains and the inrush current at power on. How high can I take this without creating a risk?
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martin manning
- Posts: 13404
- Joined: Sun Jul 06, 2008 12:43 am
- Location: 39°06' N 84°30' W
Re: Replacement Transformers
There's an element of chance at play here, which is the point on the mains power sine wave at the moment you close the switch. You could try a 2.5AT and see if that is enough. That is starting to sound like a high rating for a 50W amp, but your transformer is sized for 100W so the magnetizing current will be larger.
Re: Replacement Transformers
And also Martin, I have the additonal relay transformer to magnetize. Small current but its adding up. I did wonder whether to put the relay transformer on a separate switch.
Will get some 2.5A fuses and see how they hold up.
Will get some 2.5A fuses and see how they hold up.
Re: Replacement Transformers
Hi,
I have a question about the 125A29A/022889 OT used in most 100W versions.
I see different clones of those but it looks like they have different primary DCR.
What is the typical end to end and both halves DCR of those and are there any differences between batches (manufacturers) over the years?
Thanks in advance.
I have a question about the 125A29A/022889 OT used in most 100W versions.
I see different clones of those but it looks like they have different primary DCR.
What is the typical end to end and both halves DCR of those and are there any differences between batches (manufacturers) over the years?
Thanks in advance.