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Identifying valves with no markings

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Identifying valves with no markings

Post by Terrykc » Fri Sep 14, 2012 10:06 am

oldticktock wrote:...Then I could determine what all those valves I have where the markings have rubbed off ...

Chris, don't forget that any Philips manufactured valves (irrespective of what trademark - even a non-Philips one - they carried) you have with a two line type/date code (which is etched, so it can't rub off) can be identified.

Ignore the date code (obviously) and try to find a match for the type code from others in your stock, if you have them, or Google for on-line lists.

You can often partially identify a valve from its internal construction but there is nothing else to help you differentiate E, P & U (ECL82, PCL82, UCL82, for example) variants of the same valve!
Last edited by CTV on Tue Nov 05, 2013 7:55 am, edited 3 times in total.
Reason: Split from Marion's Bridge thread as Valve identification is another subject altogether.

 
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Re: Can anyone tell me what this says?

Post by Michael Watterson » Fri Sep 14, 2012 11:08 am

Terrykc wrote:You can often partially identify a valve from its internal construction but there is nothing else to help you differentiate E, P & U (ECL82, PCL82, UCL82, for example) variants of the same valve!


Heater resistance? I've used that to help identify. Note it's very much lower cold than hot. A connection to 6V PSU with measure of current is a confirmation.

Make a table of cold resistances vs E, P, U versus rest of ident for common type. Note that there is some variation. But the differences are large for valves of same type.

B7G types can be 1.4, 2.8, 6, 12 or more (there are some series versions).
Noval & Rimlock usually 6V or 12V or anything higher for serial types

Some kinds are very distinctive construction. Others have an outer screen that hides everything and the same type can have solid, perforated slightly, loads of holes or Mesh like screen.

Then for final verification test it on a manual tester. NOT the HST. Because you want to start at a MUCH more negative grid volts. Then assuming valve emission is OK, the grid volts (vs correct g2) will identify which identical pin out RF/IF pentode it is. Or other types similar pin outs.

Some similar parts have g3 separate or connected to Cathode. Having decided for instance that something is a DF91, DF96 or DF97 the filament resistance is much less on Dx91/Dx92/Dx94 types than Dx96 or DF97. The DF97 has g3 on a separate pin on DF91/DF96 it's to filament. You can tell on the valve tester as the current will change switching the g3 pin to filament/cathode or anode (set to 12V for this with g2 at 45) on DF97 but on the others it's a "no connection" pin.

Al lot of unmarked valves can be identified if you have DMM, table of resistances of filaments, data sheets and photos or known samples to compare. More can be verified with a non-HS tester (where you can select all valve pins & voltages manually). On valve tester if in doubt start with -15V g1, lowest filament volts, +45V g2 and +12.5 to 20V for Anode.

 
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Re: Identifying valves with no markings

Post by CTV » Fri Sep 14, 2012 12:22 pm

Interesting advice chaps and food for thought.

The picture below shows the extent of my issue I have another five boxes with as many if not more, all without markings.

I've often searched for these elusive etch codes and have to say I hardly ever find them. I did find a couple of valves which had codes "B6L" on one, another had B91 on the side near the bottom. A few have a number etched on the underside in the middle of the pins like "10". like I say the vast majority don't. Unfortunately not having had years in the trade I cannot recognise valves, well I can now recognise an EF80 or EHT rectifier perhaps a PCF80 at a push but other than that no hope of visual identification.

valves.jpg

 
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Re: Identifying valves with no markings

Post by Valvebloke » Fri Sep 14, 2012 2:20 pm

OK then, here's an exercise for a long, dark winter's evening:

Design a box of electronics driven by a computer programme which will allow you to plug an unknown valve into, say, the B9A socket on the top and which will chunter through a sequence of tests at the end of which it will have identified the valve, or at least have narrowed the possibilities down a fair bit :=D . Bear in mind that you'll occasionally be presented with a duffer, say with internal shorts or full of air. How far do you think you could get ?

More realistically, Chris, if the membership were to measure the cold heater resistances of valves in their possession would you be happy to put a table of the results somewhere on the site ? It would be most useful if it was arranged by increasing resistance so people with unknown valves could measure theirs and then 'just' look them up. The number of times I've been at a boot sale and seen what might have been an EL37 (bingo !) but might equally have been an EL33 :sad: ...

VB

 
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Re: Identifying valves with no markings

Post by CTV » Fri Sep 14, 2012 2:27 pm

Valvebloke wrote:Chris, if the membership were to measure the cold heater resistances of valves in their possession would you be happy to put a table of the results somewhere on the site ?
VB


On the main web-site yes :thumbr:

 
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Re: Identifying valves with no markings

Post by CTV » Fri Sep 14, 2012 3:11 pm

Here are only a few that had any etch codes
vlv.jpg

 
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Re: Identifying valves with no markings

Post by Refugee » Fri Sep 14, 2012 3:28 pm

I would apply a bench PSU to the heater and set it by eye and note the closest common voltage.
Then measure it like a transistor of FET in order to identify the terminals with an AVO with a good 15V battery.

 
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Re: Identifying valves with no markings

Post by Valvebloke » Fri Sep 14, 2012 3:46 pm

The Philips/Mullard codes are here http://frank.pocnet.net/other/Philips/P ... ListAB.pdf and the Brimar codes are here http://myweb.tiscali.co.uk/g8hqp/audio/brimarcodes.html.

If the valve is Mullard the first line will usually be 2 digits for the valve type followed by another digit for the version.

On quite a few of yours only the second line appears to be visible. This typically starts with a B for the Mullard Blackburn plant, then a number of the year, then a letter for the month, then (sometimes) another number for the week.

Having rotated the pic 90 degrees so I could read it more easily my best efforts are:

1451 B1 or I451 B1 - Don't know ?
W12 or WI2 B1B4 - Mullard PCL86 (W1 is the code)
VX5 B1E5 - Mullard PCL85 (VX)
IE5 2242 - Brimar ECL82 (2242)
WS2 D1J - Valvo ECL86 (WS) although to be honest I'm not sure it looks like an ECL86
7E1 B7C - Mullard PCL82 (7E)
VX8 B5A3 - Mullard PCL85 (VX)
The rest we just know are Mullards.

Incidentally a bright light and a magnifier can be a really big help when it comes to reading these codes.

VB

 
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Re: Identifying valves with no markings

Post by Michael Watterson » Fri Sep 14, 2012 4:09 pm

Having loads to hand that still have the numbers (to compare) + DMM for heater and a valve tester helps.

My "payment" for borrowing the VCM163 was to identify and sort several hundreds of valves, some with damaged or no marking. Same part valves (even if different number Mazda/RCA/Mullard/Services) were "bagged" in cheap "ziploc" type freezer and sandwich bags with ALL the possible part numbers on the front.

Amazingly few unmarked tubes were not identified and if he didn't have about 7,000 valves, most of them likely could be identified given time.

A low emission RF / IF pentode of one kind can look like a "good" RF / IF pentode of another kind, there are a lot of EF9x family! But as with transistors if the characteristics do what you want for the socket it doesn't matter what it said on glass originally.

Also some valves are the same one tested to different limits and others are the same valve with different name and datasheet for marketing reasons (if the G1, G2 and Anode volts are the same, the current *is* the same but the data sheets may have different G2 operation points).

 
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Re: Identifying valves with no markings

Post by Valvebloke » Fri Sep 14, 2012 6:38 pm

Here are a few cold heater resistances to get us going. I started with my ECL8x's. I measured them on the 200 ohm range on my LCR meter (Tenma 72-8155, not much above a basic DMM in fact). I subtracted the 0.2 ohm reading I got when I clipped the ends of the test leads together. I made the measurements directly on the valve pins, not in a base.

Mullard ECL80
6 of these measured 3.0, 3.1, 3.2, 3.2, 3.1, 3.2 ohms
So the average value was 3.1 ohms

Mullard ECL82
12 of the OG-coded version, including one branded Mazda, all measured 1.4 ohms
So the average was 1.4 ohms
1 of the fK-coded version measured 1.2 ohms

Zaerix ECL82
1 of these, with the characteristic 'Russian' sharp pins, measured 1.4 ohms

Brimar ECL82
4 of these, including one branded Pinnacle, measured 1.3, 1.3, 1.2, 1.2 ohms
So the average (rounding up) was 1.3 ohms

Zaerix ECL83
1 of these measured 1.7 ohms

Mullard ECL86
7 of these, including one uncoded Brimar which looked identical to the Mullards, all measured 1.5 ohms
So the average was 1.5 ohms

Unbranded ECL86
5 identical late-production ones measured 1.4, 1.3, 1.3, 1.3, 1.3 ohms
So the average was 1.3 ohms

I then went on to measure some U-series valves

UF41 Mullard 20.6 ohms
UBC41 Mullard 21.9 ohms
UCH42 Elpico 21.9 ohms
UY41 Mullard 48.3 ohms
UL41 Cossor 68.2 ohms
UF89 Mullard 22.1 ohms
UCH81 Mullard 31.7 ohms
UF80 Mullard 32.0 ohms
UABC80 Mullard 46.1 ohms
UY85 Mullard/Philips coded 65.0 ohms

VB

 
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Re: Identifying valves with no markings

Post by Michael Watterson » Fri Sep 14, 2012 7:13 pm

:thumbl:

I think normally no chance of confusing UL84 and EL84 etc .. :)

Parallel 1.4, 4V, 6.3, 12V heaters (D, A, E types) the higher power valves are LOWER resistance (heater power = (V x V)/R as voltage is constant)

C, U and P type series valves higher power types have HIGHER resistance (heater power P = I x I x R as current is constant)

 
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Re: Identifying valves with no markings

Post by CTV » Fri Sep 14, 2012 7:28 pm

For a quick reference test against your results.

Meter Fluke 75
Mullard ECL80
Meter Zero'd 00.0 when probes joined.
Tested 10 all 3.2R

I have to admit I don't quite understand what we are doing here. Surely other similar valves will have the same heater resistance. I cannot see how identifying a valve by it's heater resistance alone will suffice or have I got the wrong end of what we are trying to do here.

 
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Re: Identifying valves with no markings

Post by Michael Watterson » Fri Sep 14, 2012 9:26 pm

The resistance of heater just tells you if
a) PCL vs ECL Vs UCL ( they are distinctive dual height innards, further test to see if 82 or 86 etc) or UL84 vs EL84
OR
b) Signal / diode type vs Power out / Power Rectifier (Power types are lower resistance on parallel types, higher resistance on series types) though most power types are taller bottles or otherwise look different.

Examination of the heater pins to electrodes you can see difference of B7G indirect and B7G direct types. But again the heater resistance is different. On many types the cold resistance is about 1/3rd or less of Hot resistance.

ECL80 is only 300mA compared with 780 mA for ECL82 (hence PCL82 16V @ 300mA ) The ECL82 will have lowest resistance (about 1/2 of ECL80 when cold) and PCL82 will have about 2 times ECL80 heater resistance. Higher power tubes from same era always take more heater current. Series types are almost x5 to x10 the resistance of parallel versions.

Filament resistance is just another tool along with examination. On most valves designed after 1937 the outer metal isn't the anode (It is on older ones, especially if they are metallised), but a screen. So seeing which base pin it goes to can help. Often you can make out the K, g1, g2 g3 and anode etc connections at base to pins on all glass types.

 
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Re: Identifying valves with no markings

Post by GlowingAnode » Fri Sep 14, 2012 10:13 pm

Here's an idea for checking B9A valves.
Connect a bench power supply to pins 4 and 5.
Set constant current limit to 100mA.
Measure p.d. with valve inserted, if it's greater than 6.3V, then it's a Ux8x or 10xxx
Retest remainder at 300mA, again if it's greater than 6.3V, it's a Px8x or 30xxx
Remainder most likely Ex8x.
Do not try the method with ECC81/2/3's which are quite easily identified any way.
Rob.

 
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Re: Identifying valves with no markings

Post by Terrykc » Sun Sep 16, 2012 6:17 pm

Valvebloke wrote:
1451 B1 or I451 B1 - Don't know ?
W12 or WI2 B1B4 - Mullard PCL86 (W1 is the code)
VX5 B1E5 - Mullard PCL85 (VX)
IE5 2242 - Brimar ECL82 (2242)
WS2 D1J - Valvo ECL86 (WS) although to be honest I'm not sure it looks like an ECL86
7E1 B7C - Mullard PCL82 (7E)
VX8 B5A3 - Mullard PCL85 (VX)


Just a brief comment on the date code section of the above from a pub in North Lincs ...
drink.gif
Cheers!
drink.gif (9.76 KiB) Viewed 4307 times


Generally, three digit codes are 1950s, 4 digit codes are 1960s (dunno what happened after that!)

First - letter/symbol = factory (B = Blackburn)
Second - number = last digit of year
Third - letter = month (A = January, etc)
Fourth - number = week number in month

Thus B1E5 = made in Blackburn, 5th week of May, 1961

I'll be able to look at this thread in more detail after I get home ...

drink.gif
Cheers!
drink.gif (9.76 KiB) Viewed 4307 times

 
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Re: Identifying valves with no markings

Post by Goleudu Gwyn » Wed Oct 24, 2012 6:30 am

I posted up a little project of mine in the VR forum entitled "The Valve Interrogator". It's a device that, when you plug a valve into it, will give an indication of which valve pins are connected to each other. The heater pins are connected via the filament, obviously, but there may be other internal connections which will show up on the Interrogator. This may help to identify the valve but if it doesn't, it will at least check for heater continuity which will at least save fiddling with holding meter leads on the valve pins.

This, along with measuring the filament cold resistance and a visual check, should help with valve identification. The circuitry involved is very simple with nary a microchip or lines of code in sight.

 
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Re: Identifying valves with no markings

Post by Refugee » Wed Oct 24, 2012 10:52 am

I have given this topic a bit more thought as it has developed.

*** I suppose i had better just say that i am testing a fully screened valve with no chance of looking at the internal structure for this exercise. ***

With heaters one thing that has not been looked at yet is the increase in resistance as the valve heats up to the correct temperature.
This could be tested for different envelope types and periods of manufacture in order to estimate the voltage by measuring the temperature related increase in resistance as a percentage for a number of known valves.
Start with 0.5 volts as some heaters can be as low as this in things like hearing aids.

Keep the results in a table :idea:

Cathode location would be next.
First make sure that a high ohms range does not pick anything up from any other pins with the negative probe connected to the heater with the heater still on. This proves that it is indirectly heated.

If this is the case then connect a 100K resistor to the high output of a signal generator and connect the other end to the high end of a scope probe and common the earths.
With the heater off connect the earth to the heater pins and dab it on each pin and note how much it is shunted by the cathode to heater capacitance. The greatest shunting effect will identify the cathode pin. This is not required if it was identified as directly heated.

If there is no easy connection to the external screen just slip a foil covering over the envelope and connect this to the low side if the test probe and repeat the shunting effect test and note the two pins that show the greatest shunting effect in order to identify the screen and anode.
If there is an obvious screen on the envelope just measure it on an ohms range to find the pin.

Next with the same 100K resistor apply DC voltage in place of the signal generator to it and turn on the heater and measure the shunting effect starting at about 60 volts with a DVM.
No shunting effect identifies that there is an internal screen present and that the other electrode that showed a strong shunting effect is the anode and transferring the probe to it should confirm this.

Now just measure all the other pins and hopefully they will just act like dropper and some idea of grid spacing between cathode and anode can be estimated from the voltages using a DVM.
Any pins that did show a shunting effect that fail to show voltages on this test can be tested again as a separate active element on a common cathode with the already identified pins noted and eliminated from the remainder of the test.

If the internal structure can be seen some short cuts can be taken.

At least this should give a good idea of the pin out.

 
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Re: Identifying valves with no markings

Post by Dr Wobble » Mon Nov 05, 2012 5:34 pm

I read a post some time back that said something on the lines of,if you apply a moist/damp cloth to the unmarked valve,under a good light,it may be possible to decipher the erased print. So far every suggestion to identify the valve has been based on its electrical values.Might it be possible to read the original print by using chemicals or ultra violet/infra red light? Just a thought,Andy.

 
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Re: Identifying valves with no markings

Post by Valvebloke » Mon Nov 05, 2012 6:24 pm

I wouldn't touch the valve with anything wet like a cloth. Many of the inks wipe off very easily. What you can try is cooling the valve in the fridge and then either allowing mist to condense on it naturally or breathing mist onto it. That will occasionally show up a hidden mark. It works best as the mist is evaporating when it can stay 'stuck' to the mark slightly longer than to the plain glass. But in my experience this still isn't a very effective technique. Nothing is quite as good as a magnifier combined with the brightest possible illumination (bright outdoor daylight, for example). Placing something dark behind the valve can sometimes help too as can looking obliquely at the glass rather than straight on.

VB

 
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Re: Identifying valves with no markings

Post by CTV » Mon Nov 05, 2012 6:30 pm

I have a box of about 150+ TV valves with the markings rubbed off.

Believe me when I say I have tried all the sensible suggestions and even the old wives tale ones, from the freezer to the ultraviolet LED torch and everything in-between, none worked for me.

However since VB posted the etching codes with the data, I have managed to identify many of them so that is the best method as far as I'm concerned.

Note:

Maybe certain valve envelopes (20 & 30's ?) and certain inks used respond to the other methods. Most of my valves are B9A & B7G TV ones they certainly do not seem to.

Not all valves have the etching codes.

Chris

 
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Re: Identifying valves with no markings

Post by freya » Tue Nov 20, 2012 10:46 am

I wasnt sure where to post this but here goes,

My latest buy is a taylor 94a waveform and alignment generator, it had been robbed of its ECC83 valves for obvious reasons. As i knew i had a load in a box i bid and got it for the starting price. My problem is that on looking in my box of double triodes has lots that have no markings, is there an easy way of finding out if they are ECC82`s or ECC83`s by looking at the contsruction.
I know the ECC83 draws more anode current.


Stephen

 
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Re: Identifying valves with no markings

Post by Valvebloke » Tue Nov 20, 2012 11:11 am

I'm afraid not. Here are four ECC83s from three different manufacturers

ECC83s reduced.JPG


They look as different as, well, four very different things.

The trick is usually to find the etched factory codes (see above). Beyond that you'll have to test them.

Actually for a given anode and grid voltage the ECC82 draws more current than the '83 (e.g. 250V, -8.5V, 10.5mA for the '82, 250V, -2V, 1.2mA for the '83).

VB

 
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Re: Identifying valves with no markings

Post by freya » Tue Nov 20, 2012 12:30 pm

Would a low emission ECC82 test like an ECC83 though ?

stephen

 
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Re: Identifying valves with no markings

Post by Valvebloke » Tue Nov 20, 2012 1:34 pm

It'd have to be very low emission indeed and you'd have to be particularly unlucky to find that both halves had degraded to the same extent, so they both looked like a good ECC83. Valves that sick are usually on a rapid downhil path. If you have enough ECC83s you may be able to compare the internals of a blank one with a known ECC83. I'm not saying every single valve is different from every other one - obviously they are not. It's just that there are quite a lot of different types of ECC83.

VB

 
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Re: Identifying valves with no markings

Post by freya » Tue Nov 20, 2012 3:50 pm

Thanks, i now have two piles, one of ECC82 One of ECC83 :D

That was fun

Stephen

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