Old Weller Magnastat Iron Transformer Buzz

[zaraxisof]

Hello everyone. I recently found a nice old Weller Magnastat TCP 24 50W iron with transformer base box at local flea market for 10€ so i didn't let the chance go away.

It's exactly like the common green/blue Magnastat line but seems a bit earlier, probably from late 70s. Iron's handle is black and 24V transformer box dark blue.
Type 21 021 - TCP 24V 50VA.

The iron works well and do its job. Came with a "7" tip code type (370 C), measured the temp and it gets stable at about 360-380 C, so seems ok. You can clearly hear clicking sound from switch.
For those who may don't know how they work, these are common Magnastat (Weller patent) irons with fixed controlled temp. Their mechanism is based on Currie Phenomenon.
https://hackaday.com/2016/06/01/long-term-review-weller-magnastat-soldering-iron/

The transformer just provides the iron with 24VAC, nothing else. Not temp control stations here. The temp has only to do with the tip number type you use (types 6,7,8 are the most common). For type 7 you get 370C.

My main concern is that the 24V transformer is noisy, laminations buzz pretty loudly. The trafo is unpotted.
Is it smthng to worry about or just aging loose laminations buzz common issue?
I was thinking of wax potting or putting it in a dedicated electrical varnish bath to eliminate.

Any thoughts?

 

[guitar_paul1]

If it draws the right amount of current I wouldn't worry if it were mine. I've cured xfrmr buzz by wedging a judicious piece of fish paper under the bell cover, if it has one. Worth a try.

 

[Jon Snell]

I used 12 of these on my workshop benches, one for each engineer from the mid 80's until I retired.
There was one that buzzed, due to loose laminations but never gave any trouble.
I would say that your 'new' iron will probably outlast your days with only worn out bits to worry about.
I sold all of my Weller equipment back in 2015 and apart from wear and tear, they were all perfect.
The tips are not keen on lead free solder, they tend to lose the tinning quite quickly.

 

[zaraxisof]

If it draws the right amount of current I wouldn't worry if it were mine

Will try to measure current the iron draws and report back later. I guess it should be 0.5-2A or so, then "click" and zero Amps , then again .... Right?

The tips are not keen on lead free solder, they tend to lose the tinning quite quickly

Yes i know, no lead free solder to worry about here. I'm using standard 60/40 2.5% Stannol HS10 1mm solder wire since 2004 with no problems at all. Only old techniques for mojo!

I've cured xfrmr buzz by wedging a judicious piece of fish paper under the bell cover, if it has one. Worth a try.

Nice input but no bells used there.
Any other recommendations for eliminating lam noise?

 

[Wally]

You might try tightening the construct. The laminations might be loose.

 

[zaraxisof]

I have tightened the four screws but didn't cure the noise.

Anyway, smthng weird happened just now. I was about to measure the current the iron draws, had my multimeter probes at the two screw terminals (two wires that go to the iron cable). Red probe at A range, black at COM as usual and turned the knob at A (amperes) AC range.
Turned the transformer box power switch on and boom, blown fuse !

Why this happened?
The box works w/ everyday use since one week many hours per day, so this should do with multimeter? Did i make smthng wrong?

Fuse is ESKA branded. And says "M0.63/250C".
Is this 630mA 250VAC?

EDIT: Quickly replaced with a 0.5A slow blow (until i find a 0.63A) and box works fine again.
It was probably caused because the box accidentally dropped on the desk, and as i checked with continuity test smthng wwird had happened with the spring inside fuse holder. Was a bit out of place, so that could explain why fuse exploded.

 

[zaraxisof]

Again, tried to measure current with multimeter and blew the new fuse. Why this happens?

 

[Jon Snell]

Place your meter in series not parallel.
The bobbin is loose on the laminations, not the laminations are loose.
If you need to, mix up some epoxy and place it around the bobbin where it contacts with the laminations.
Fit a 63mA 250v T fuse NOT a 0.63A as you wrote!

 

[zaraxisof]

Fit a 63mA 250v T fuse NOT a 0.63A as you wrote!

Fuse says M 0.63 so i think it's a 0.63A (630mA) slo blo, not 63mA. If I'm wrong correct me.

Place your meter in series not parallel.

that happens when you troubleshoot while recovering from last night's hangover.

If you need to, mix up some epoxy and place it around the bobbin where it contacts with the laminations.

nice tip will try this.

 

[Jon Snell]

630ma is the correct value, my mistake.

 

[SoK66]

I have this issue with a 5E8-A clone I built about nine years ago. It's a collection of sourced parts, but the PT is Mojotone's earlier spec'd high power Twin unit. Gives off a faint hum that doesn't come through the speaker. Not worth fixing, works fine and the amp sounds like heaven otherwise.

 

[zaraxisof]

Installed a proper 0.63A ceramic slow blow T fuse, replaced the old slightly cracked Rifa 10nF X2 anti-arcing switch cap with a new Pilkor one. If you are also into r2r tape decks like Revox's or other old gear that use them you may know the common issue with Rifa's - just google "Rifa smoke / explode". The old Rifa measured 63nF instead of 10nF.
Also bought a new genuine Weller proper replacing tip, type 7, long chisel , the same as used, just a fresh one. It's nice that for 5 bucks you can still find them today. If you are careful and treat them well they can last long.

The iron works perfectly for now, hope for many years to go.
Don't bother with trafo's noise for now, after closing the enclosure box and put it aside in its place on desk seems it isn't so loud for my ears any more. In the end of the day, I'm always soldering while listening to music.
If gets annoying in the future i will try some methods mentioned.

It's a real and strong beast, cannot be compared to my other "40-50W" 936 Hakko clone or other Chinese irons i own in terms of heating, strength and power.
Hope it will be reliable as the heating element/switch are a bit pricey.

After so many years it was time to get a real tool in my hands. Fast, strong, clean, ultra shiny solder bombs in comb with my trusty 60/40 Stannol wire.

Cheers people