Valve Testing - UK Vintage Radio Repair and Restoration Discussion Forum

Valerwee · 2nd Jun 2021, 2:47 pm

Hi

I've got some Mazda PP5/400 Valves and was looking for some advice to how / who i can get them tested by please?

Radio Wrangler · 2nd Jun 2021, 3:24 pm

They are easily tested in the sets they belong to. Just a quick check of the anode current they are running at and the grid bias voltage will tell you whether they're OK.

It saves on all the risk of handling/shipping them and is definitive in terms of whether they're OK in their set.

These are pretty rare valves, replacements are hard to get and the audiophool fraternity have pushed the prices up to astronomical levels.

David

David Simpson · 2nd Jun 2021, 5:51 pm

If these valves were a speculative acquisition & not out of a radio or amplifier that you own, then in all honesty you'll need to get them tested on a decent VCM( by a knowledgeable/experienced person), prior to flogging them. (£££'s in your eyes ?).
I'll echo David's post - these are jolly rare Power Triode valves. Avoid at all cost Royal Mail or any other Postal/Courier service, unless you wrap them with several inches of Rocking Horse Manure & plenty of bubble wrap!
I tested a number of these types of triodes plus other DE & BE valves(£2K +) from the same era(1920's/30's - 90 years old !), a while ago. BUT - they were hand delivered & collected by a BVWS chum - the owner, who lived about 30 miles away. All I charged him was the cost of an extra pair of underpants.
The London area must be awash with valve testing enthusiasts.

Regards, David

2nd Jun 2021, 6:14 pm

I knew some "audio fool" valves where expensive, but 2k, that's taking a whole packet of Hob Nobs. Modern valves that are still being made are much better in all aspects. As David said, just measure in circuit or don't bother if it works.

Radio Wrangler · 2nd Jun 2021, 7:25 pm

At those prices few private individuals would test them for you out of fear of liability. Only someone with a commercial repair operation is likely to have liability insurance in place, and they would see it as a business transaction and would expect to see a proportion of the apparent gain in value due to the testing.

The radio restorer has it easy, testing in situ is just fine.

David

David Simpson · 3rd Jun 2021, 5:05 pm

Hey MM - 'twasn't £2k for one heffing Triode - about 40 odd valves in a well padded big plastic box. As well as PX25 types, some were cruciform, and there were one or two KT's. £2k is what all of them might have realised on eBay, going by their average prices at the time. When I opened up my pal's box, some of the valves were in their original NOS boxes and some just wrapped in plenty of old paper towelling, which, after testing, I put into some of Pamphonica's great "flat-pack" new boxes.
I just mention this so that Valerwee understands how much care needs to be taken with such rare valves. Thankfully I didn't phook any of my pal's valves, but its not something I do, or would do, commercially.
I have, very occasionally, Ebay'd one or two of these NOS rare old power triodes, but(as folk who ken me know) they were all flogged along with an A4 Gm graph. Whether folk are audiophools or not, I would recommend that you shouldn't buy such hexpensive valves without a graph. After all, back in the 20's & 30's many such power triodes, and later BT's & Pentodes, all came with a graph printed on the side of the box or folded up inside.
(Buying a valve online, with the small print saying - "AVO VCM Tested", sometimes means SFA!).

Regards, David

bluepilot · 3rd Jun 2021, 5:11 pm

Quote:

Originally Posted by David Simpson

Buying a valve online, with the small print saying - "AVO VCM Tested", sometimes means SFA!

I have seen many valves for sale with small print, or even large print, saying that the valve has been tested on this, that or the other valve tester. Unfortunately they often omit to say whether the result of the test was good or bad.

John_BS · 3rd Jun 2021, 5:16 pm

Quote:

Unfortunately they often omit to say whether the result of the test was good or bad.

Practising prior to entering politics!

Heatercathodeshort · 3rd Jun 2021, 7:30 pm

The case of the 'half heater' with PX4 and PX25 valves is a very real one. personally I would much rather buy new replica valves. They are very good quality.
I certainly would not spend hundreds of pounds on second hand junk and even if they tested good they would probably have a limited life. Just my thoughts. John.

2nd Jun 2021, 2:47 pm	#1
Valerwee Diode Join Date: Jun 2021 Location: London, UK. Posts: 1	Valve Testing Hi I've got some Mazda PP5/400 Valves and was looking for some advice to how / who i can get them tested by please? Last edited by Cobaltblue; 2nd Jun 2021 at 2:51 pm. Reason: % becomes 5

2nd Jun 2021, 3:24 pm	#2
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,857	Re: Valve Testing They are easily tested in the sets they belong to. Just a quick check of the anode current they are running at and the grid bias voltage will tell you whether they're OK. It saves on all the risk of handling/shipping them and is definitive in terms of whether they're OK in their set. These are pretty rare valves, replacements are hard to get and the audiophool fraternity have pushed the prices up to astronomical levels. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

2nd Jun 2021, 5:51 pm	#3
David Simpson Nonode Join Date: Mar 2008 Location: Aberdeen, UK. Posts: 2,851	Re: Valve Testing If these valves were a speculative acquisition & not out of a radio or amplifier that you own, then in all honesty you'll need to get them tested on a decent VCM( by a knowledgeable/experienced person), prior to flogging them. (£££'s in your eyes ?). I'll echo David's post - these are jolly rare Power Triode valves. Avoid at all cost Royal Mail or any other Postal/Courier service, unless you wrap them with several inches of Rocking Horse Manure & plenty of bubble wrap! I tested a number of these types of triodes plus other DE & BE valves(£2K +) from the same era(1920's/30's - 90 years old !), a while ago. BUT - they were hand delivered & collected by a BVWS chum - the owner, who lived about 30 miles away. All I charged him was the cost of an extra pair of underpants. The London area must be awash with valve testing enthusiasts. Regards, David

2nd Jun 2021, 6:14 pm	#4
Guest Guest Posts: n/a	Re: Valve Testing I knew some "audio fool" valves where expensive, but 2k, that's taking a whole packet of Hob Nobs. Modern valves that are still being made are much better in all aspects. As David said, just measure in circuit or don't bother if it works.

2nd Jun 2021, 7:25 pm	#5
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,857	Re: Valve Testing At those prices few private individuals would test them for you out of fear of liability. Only someone with a commercial repair operation is likely to have liability insurance in place, and they would see it as a business transaction and would expect to see a proportion of the apparent gain in value due to the testing. The radio restorer has it easy, testing in situ is just fine. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

3rd Jun 2021, 5:05 pm	#6
David Simpson Nonode Join Date: Mar 2008 Location: Aberdeen, UK. Posts: 2,851	Re: Valve Testing Hey MM - 'twasn't £2k for one heffing Triode - about 40 odd valves in a well padded big plastic box. As well as PX25 types, some were cruciform, and there were one or two KT's. £2k is what all of them might have realised on eBay, going by their average prices at the time. When I opened up my pal's box, some of the valves were in their original NOS boxes and some just wrapped in plenty of old paper towelling, which, after testing, I put into some of Pamphonica's great "flat-pack" new boxes. I just mention this so that Valerwee understands how much care needs to be taken with such rare valves. Thankfully I didn't phook any of my pal's valves, but its not something I do, or would do, commercially. I have, very occasionally, Ebay'd one or two of these NOS rare old power triodes, but(as folk who ken me know) they were all flogged along with an A4 Gm graph. Whether folk are audiophools or not, I would recommend that you shouldn't buy such hexpensive valves without a graph. After all, back in the 20's & 30's many such power triodes, and later BT's & Pentodes, all came with a graph printed on the side of the box or folded up inside. (Buying a valve online, with the small print saying - "AVO VCM Tested", sometimes means SFA!). Regards, David

3rd Jun 2021, 7:30 pm	#9
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Valve Testing The case of the 'half heater' with PX4 and PX25 valves is a very real one. personally I would much rather buy new replica valves. They are very good quality. I certainly would not spend hundreds of pounds on second hand junk and even if they tested good they would probably have a limited life. Just my thoughts. John.