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Backtoreality 16th May 2018 11:57 pm

EBC33 valve
Hi folks,
While in the process of refurbishing my Bush DAC90 I collected some valves to try out. Not having a working valve tester I thought I'd just do a quick heater continuity test on each of the valves. They all checked out okay except for an EBC33 which was open circuit, or so it appeared! On closer inspection I noticed there was no solder on the bottom of the valve pins. Pushing my multi-meter probes into the ends of the heater pins, to touch visible wires, gave me a continuity reading!
Is it possible that Mullard just forgot to solder the pins? All of the other valves I collected together for the set have soldered pins!

paulsherwin 17th May 2018 12:06 am

Re: EBC33 valve
You do find these manufacturing faults occasionally.

Boater Sam 17th May 2018 6:40 am

Re: EBC33 valve
I always try resoldering the pins if I find an O/C heater. Some valves with a high current heater regularly have gone O/C and come back to life with a soldering iron.

turretslug 17th May 2018 4:28 pm

Re: EBC33 valve
It's not uncommon with IO and similar base valves- the leadout wires may have been heated and therefore a little tarnished during the bulb processing and sealing, and the soldering at the end of the hollow pins may have been both cursory and minimalist. I've often found dry-looking joints with just a tiny amount of solder in the end of the hollow pin, and that rectifiers with their high current heaters seem particularly prone to joint iffiness.

Argus25 17th May 2018 11:06 pm

Re: EBC33 valve

Originally Posted by turretslug (Post 1044267)
the soldering at the end of the hollow pins may have been both cursory and minimalist.

That is a good way to put it. Some I have seen, the soldering itself only coated or tinned the cut cross section of the wire, presumably it was cleaner there and connected to very little of the length of the wire's surface. Then with heating and cooling the wire ultimately disconnects itself or goes intermittent. I had a 6J5 once where its heater would go on and off at times because of this.

The same soldering defects can also occur on plate and grid top caps. One radio I owned with a 6k7 in the IF had an intermittent grid connection here, it took weeks to find what the cause of the trouble was the very first time I encountered it.

Backtoreality 19th May 2018 6:53 pm

Re: EBC33 valve
1 Attachment(s)
Well I've cleaned and soldered the ends of the pins and now have a fully functional EBC33 again working happily in my Bush DAC90. I couldn't see any evidence of previous soldering. Hopefully I've attached a photo of the pins of both my EBC33s to this post so you can see what I mean.

chriswood1900 19th May 2018 8:05 pm

Re: EBC33 valve
Pity they don't include the day of the week in the batch code it would probably show as produced on a Friday!!

HamishBoxer 19th May 2018 8:49 pm

Re: EBC33 valve
Pic 1 looks like it was never soldered.

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