EZ80 fails straight out of the box

[Cobaltblue]

I was checking a Philips set over and the EZ80 was down to air.

Without the rectifier the set was allowed to warm through a bit and after an hour no sign of stress from the transformer and the lamp limiter was only just glowing.

Most of my accessible parts stores are in Poole so I had a search for a stray.

In the loft I found a boxed 6202 brand EZ80 it looked new and the valve in the box was the same as the box.

I considered it was probably a new valve.

However on fitting it the lamp limiter immediately lit up, and I mean immediately no time for any of the heaters to start warming up.

I removed the valve and did some cold checks there was a short circuit between pins 1 (Anode) and 3(Cathode) and the filament was open circuit.

Pin 4 filament was also short circuit to pin 3 (cathode)

So what do we think was this valve simply put back in the box after failing? or was it faulty since manufacture?

6202 is probably a re-brander.

Using a magnifying glass you can see damage to to the cathode tube in the region between the two anodes.

This must have caused quite a firework display.

This valve has been in my loft untouched for more than 25 years and is with other boxed valves (mixed brands). I shall treat the rest of these with caution.

The pictures show the 6202 and the original Miniwatt (down to air)

Now I am off to search for another EZ80

Cheers

Mike T

[Nuvistor]

I reckon it was faulty from new. I don't know the 6202, brand whether it was a decent rebrander and this was unfortunate or if they bought seconds very cheap and happily replaced any that came back faulty.
Frank

[Andrew B]

Engineers in the past put dead valves into the box that the replacement came in, very easy to pick up "NOS" in the box to find it's actually a duff. Many companies insisted on duff valves being returned to them in an attempt at stock control.

[paulsherwin]

Andrew's point is very true, but in this case I agree with Frank.

[Sideband]

6202 was a re-brand of RST Valve Mail Order Co. based in Streatham SW London....I know because they were just up the road from where I lived. Their phone number ended in 6202 hence the number on the valve. I think they bought valves from wherever they could and just put their own number on them. Probably most of it was bankrupt stock. It's quite possible that some suppliers had new valves returned as faulty that never got sent back and they will have ended up in the bankrupt stock, subsequently re-boxed and sold. It would just have been replaced back in the day.

RST were eventually taken over by Langrex who then occupied larger premises in Streatham. That operation moved down to Croydon and now they've moved to Billingshurst.

[Cobaltblue]

Thanks for the information about 6202

I have now dug a second hand EZ80 and all is well HT a bit low but I suspect that's a lot to do with the HT smothing caps I will have to see if they will reform.

Cheers

Mike T

[FrankB]

I bought about 75,000 tubes many years back and most were supposed to be NOS.
Well... they were not.
There were several batches labeled "New" that had notes in the boxes about being "defective, return to factory".
Likely Andrew is correct.
In my younger (?) years, I worked for a wholesale electronics supplier. Often tubes came in DOA from the mfg, or were damaged in transit.

[Nuvistor]

We were a small shop and didn't have many returns, although only a small number we couldn't afford to not return to the manufacturer. The BVA valves were time consuming to return, they wanted make,model number, serial number, customers name and address, date of sale. We did this at the time of changing the valve, no chance of remembering a few weeks later.
What a difference when we started to use Pinnacle valves in tbe 70's, the rep came around once a month, replenished what we had used and replaced faulty ones without question.
By the 70's, BVA makers were sourcing valves from many places and were not that different to the major rebranders.
Photo from the side of a Mullard valve box with return details
Frank

[Cobaltblue]

That's interesting Frank

Just goes to show what the cost of the valve was compared to labour rates.

Today for a business of any size it would need to cost in the order of £70 to make it worth sending back.

Cheers

Mike T

[Leon Crampin]

Your "6202" branded EZ80 has all of the hallmark signs of a Communist bloc product. The giveaways include the pointed pins and the copper colouration within the glass to metal seal.

I'm afraid I've never had much luck with these valves and actively try to avoid them now. They are either dead on arrival, develop shorts (in this case, endangering a transformer) or have unacceptable grid current in the case of output valves. The later "ECL and derived" triode-pentodes were especially bad.

The "Trabants" of the valve industry, I think.

Leon.

[John Caswell]

Mike T you have a PM

John

[Cobaltblue]

Well John you said I had a PM 4 hours ago and still waiting

Cheers

Mike T

[John Caswell]

Hi Mike,
Another PM sent at 13:15 asking you send address to my email address and I will stick an EZ80 in the post for you.

John

[John Caswell]

Hmmmm
Just looked at my "out" box and it shows nothing so....

Address to johndotcaswellatjohncaswelldotcodotuk and I will reply.

John

[PJL]

I have a 6202 EM84 which had never been unwrapped. It works but the bars are fully open (no illumination) unless tuned to a very strong station (grid -ve) . Not a brand I would recommend.