Dim Bulb Tester

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bloodtypw

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Joined 2015
#1
Hi all,

I've made myself a dim bulb tester ready to test a valve amp that I am concerned has a faulty transformer.
When I bought the amp the builder said I should never fire it up without the speaker connected. Is this the same for testing? Should I connect the speaker before testing? Also, should the valves be in place too?
Thanks in advance everyone.

Cheers, Ben
 
#8
AndrewT said:
Are there any relays around the mains wiring?
Click to expand...
Sorry AndrewT, I really am a learning amateur so I don't know. Here's a pic if it helps:
21766058374_cfb8d0cb9e_b.jpg



I clamped the two pieces of separated transfomer (the E and I sides) together and that reduced the buzz to a hum.
 
#10
AndrewT said:
I can't see any relays.
Click to expand...

Thanks AndrewT, appreciate you looking. It seems like it may be the separated sections of Transformer causing the buzz. Think I'm just going to replace the transformer to be safe. Hopefully the rest works!

With the transformer clamped the buzz reduces to a hum and the Dim Bulb Tester doesn't light up so hopefully nothing has shorted. We'll see...!

Thanks again.
 
#11
This appears to be an SE guitar amp, please confirm and I will move it to the proper place.

I see a solid state bridge rectifier, it is more likely that one of the diodes has shorted UNLESS the ballast lamp (sorry not dim bulb) does not light with no tubes installed and a known good fuse in the fuse holder. (check fuse before running test)
 
#12
Probably best if you stick to one thread so people have some background on this issue.

http://www.diyaudio.com/forums/tubes-valves/281315-newbie-broken-valve-amp-help.html

You really need to forget about that transformer, its done. Let us know which winding are connected on that transformer so we can suggest a suitable replacement. The amp looks very similar to a Fender Champ clone so it shouldn't be too difficult to find something suitable.
 
#13
my post from last thread: The gap, minimizing it, is a huge thing with transformers. You've increased this gap a large amount, I doubt it will put out as much power as it used to, and it might make lots of noise now. And that's if you haven't damaged the windings. Can you take it back to the builder? Has anything else been damaged?


believe me now?
 
#14
kevinkr said:
This appears to be an SE guitar amp, please confirm and I will move it to the proper place.

I see a solid state bridge rectifier, it is more likely that one of the diodes has shorted UNLESS the ballast lamp (sorry not dim bulb) does not light with no tubes installed and a known good fuse in the fuse holder. (check fuse before running test)
Click to expand...

Hi KevinKr, thanks for your message. I can confirm it's an SE amp. Apologies if this post is in the wrong place.

The light on the chassis lights and the fuse has not blown. I don't know if this tells us anything? How would I test the diodes?

Thanks again.
 
#15
mcandmar said:
Probably best if you stick to one thread so people have some background on this issue.

http://www.diyaudio.com/forums/tubes-valves/281315-newbie-broken-valve-amp-help.html

You really need to forget about that transformer, its done. Let us know which winding are connected on that transformer so we can suggest a suitable replacement. The amp looks very similar to a Fender Champ clone so it shouldn't be too difficult to find something suitable.
Click to expand...

Hi mcandmar. Thanks so much for your message and apologies for opening an extra thread - along with being a newbie to valve amp DIY, I'm also fairly new to forums. I'll make sure to stick to one thread next time.

The amp is indeed a Fender clone. As I understand it from the builder it is built using the Weber amps 5f2a schematic. All the components are the same, barring the master volume.

How would I find out what windings are connected? Would be great if an alternative could be suggested - that would be amazing. As before, thanks so much for the advice, it's really useful.
 
#16
cbdb said:
my post from last thread: The gap, minimizing it, is a huge thing with transformers. You've increased this gap a large amount, I doubt it will put out as much power as it used to, and it might make lots of noise now. And that's if you haven't damaged the windings. Can you take it back to the builder? Has anything else been damaged?


believe me now?
Click to expand...

Hi cbdb, I meant no offense re your last post. I've just been trying to explore all avenues. The gap is indeed large and makes a huge amount of noise. I temporarily clamped it and it reduced the noise to a noticeable hum. I have a Telefunken replacement on order but I'm interested in mcandmar's thoughts about an alternate replacement - hopefully a modern one.

I can't see anything else that has been damaged but I'm feeling my way through it and learning very slowly as to how to check what is working and what isn't. As far as I can see, only the transformer is damaged, although kevinkr thought the diodes may have shorted too. So if I get a steer on how to test them, I'll check those too.

I bought the amp quite a while ago from someone who posts on Amp Garage forums but can't find his contact details unfortunately - although I am still searching.

Thanks again for your help, I really appreciate it.
 
#19
#20
cbdb said:
my post from last thread: The gap, minimizing it, is a huge thing with transformers. You've increased this gap a large amount, I doubt it will put out as much power as it used to, and it might make lots of noise now. And that's if you haven't damaged the windings. Can you take it back to the builder? Has anything else been damaged?


believe me now?
Click to expand...
Is this confirming that the allegedly noisy transformer has already been modified?
 
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