Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TurboGuitarMelton on July 18, 2023, 01:34:42 pm
-
I recently aquired a power transformer from a Truetone D-901 radio and record player. It tests fine and has 5 and 6.3 volt filaments and a 260-0-260 HV winding.
Problem is it is rusted on the bell covers and the leads for the filaments are brittle and are cracked. The primary and the HV tap seem fine and are a different type of cloth wire so I was thinking about just replacing the filament leads.
I took the bell cover off and was going to just trim the wires, splice in new leads and double heat shrink them.
I was also thinking I could just paint the bell covers with black rustolem spray paint.
Is that safe to do? I just wanted to double check. Ive attached some pics
-
I was also thinking I could just paint the bell covers with black rustolem spray paint.
Is that safe to do? ...
I recommend sanding the rust off, and possibly some/much of the old-paint. They spray with a Rustoleum gray primer, then shoot with your color of choice after the primer dries.
No problem doing that, and what I did to get a "hammered copper" look for the transformers below:
(https://i.imgur.com/TG4Xwgz.jpg)
-
I took the bell cover off and was going to just trim the wires, splice in new leads and double heat shrink them.
That's safe to do. Scrape the varnish off the ends of the PT wires so you can get a good connection. Using flux helps clean the PT leads.
I did the same with an old 1941 PT a few years back. I had to replace all the leads. Took a while!
http://sluckeyamps.com/RCA/RCA.htm
I used HBP's painting method.
-
Awesome, Ill do that then! Thank you for the quick replies and suggestions!
-
Here by the sea we learn to look at rust.
It is 80 years old and hardly 1/10th of the way rusted through.
The rust is not doing any harm, and adds some mojo.
If it really bothers you: find dark brown oil-base wood stain, Minwax, to glue-down the loose rust that doesn't brush off easily.
(https://sherwinwilliams.widen.net/content/qpayvjzjg4/webp/70012444-14-minwax-wood-finish-2716-dark-walnut-1Q?w=100&h=100)
I put heavy iron handrail brackets, recovered from muck, in my garage, wiped with Minwax, and they are still fine to touch although very antique looking.
-
Here on the salt mine, I like to knock of all the loose stuff with a wire brush, then chuck up a sanding wheel, (lots of small squares of sandpaper) n "buff" up more, degreaser bath, then clear lacquer till the can runs dry
-
Here by the sea we learn to look at rust.
It is 80 years old and hardly 1/10th of the way rusted through.
The rust is not doing any harm, and adds some mojo.
One day, I'd like to rust-blue a chassis or endbells as a way to finish amp-metal & protect it against future (damaging) rust.
-
Replaced all the leads on the transformer. Had a few issues with wires being too thick for the bell cover to go back on and had to redo it once. Some of the wires ended up really short and are right up against the bobbin. I heat shrinked them. The heat shrink was rated for 600v so it should be fine.
I tested the transformer at a lower voltage with a power supply I have. (15v AC) Everything seems to be good to go!
In the event that a wire from the 120 AC line or the High Voltage Tap were to short to the bell cover inside the transformer what would happen? Would I get shocked? Would the 2amp fuse just blow? Or would the PT just stop working after heating up?
I guess since I have never done something like this I am a bit paranoid something could go wrong. Although I suppose a short like that could happen with any Power Transformer.
-
What fuse??? This is just a naked PT sitting on the bench. If the 120V hot wire touches the bell cover and you touch the bell cover and are barefooted on a cement floor you will get a nasty shock. Otherwise, not much will happen.
If this PT is installed in a chassis we need to see a schematic to predict what will happen.
-
I plan on using this transformer in a 5c1 champ. I am going to add a 3 wire power chord instead of the 2 wire shown.
*also there will be no death cap (.05 from the 120V AC to ground)
So the scenario would be me holding the guitar that is connected to the input jack. If a short were to happen inside the transformer while I was playing guitar would I get shocked or would the fuse protect me?
-
The ground connection on the 3 wire power cord will protect you
Franco