Valve Identification

[reely reely]

Im trying to source a Valve (ecc83) or equivalent for a particular piece of equipment, the valve in question was removed and never replaced some years ago, obtaining this valve isnt really the problem as they are readily available but my Father has a large box of valves most of which are quite obviously not the correct ones but there are a few in there that look like they maybe able to do the job, however the print has come off all the similar looking valves

My main question is, is there a way of working out from the layout and pin readings if any of the valves are suitable to fit, or is it more a case of dump them and simply obtain one which is being offered for sale ??

Thx in advance

Tim

[GrimJosef]

First, please don't dump them (unless by 'dump them' you were thinking of dumping them round at my place ). Some of them may be worth decent money and even the ones that aren't may be useful to someone here.

Identifying valves which have lost their printing comes with practice. But there are some easy things to look out for. ECC83s, for example, are double triodes which means there are two completely separate electrode assemblies inside one glass bottle. There will be clear physical space between them. You can see what I mean, I hope, from the pictures here http://www.r-type.org/exb/exb07158.htm. They are all ECC83s or 12AX7s, which are very close equivalents, just made by different manufacturers. Of course there are other double triodes - ECC81, ECC82, ECC88 are all quite common - and it can be tricky to tell these apart just by looking. But at least if there are no double triodes in your father's collection you should be able to establish that.

Sometimes, if you look very carefully, you can see a factory/date code etched into the glass - typically a few letters and numbers. If the first two characters are I6 then that's the code for the Philips (Mullard, Amperex, Valvo, Dario, Miniwatt) ECC83 (the full list and explanation is given here frank.pocnet.net/other/Philips/PhilipsCodeListAB-v8.pdf). Beyond that you have to start looking at the arrangement of pins sticking up through the internal mica supports to try to establish what type of valve(s) is (are) inside the bottle. But now you're getting into serious detective work.

Cheers,

GJ

[Boater Sam]

Hi.
You can do a lot of detective work!

Compare the internal structures. It is usually possible to see the supports and connections to the anode/s, heater/s and cathode/s. Maybe even the grids.
Compare these with the data sheet for the valve you need. Are they connected to the same pins? No extra connections to pins?

Measuring the heater resistance is not really any use as the cold resistance will not allow you to calculate the voltage or current.
ECCxx series will be a twin heater, 6.3v. Putting 6.3 v on the valve heater pins should bring the heaters up to temperature. Measure the current and see if it agrees with valve data. If not and the heater can be measured on an ohms meter the valve may be PCCxx series.

Physical size should be similar to data sheet too.

Infra-red light will usually show up the original markings with luck, try the valves under a banknote checker.

If you are happy that the components inside are connected where they should be and you cannot find any obvious differences between the data sheet and the valve you are examining, fit the valve, run the chassis up with a series 40watt or 60watt bulb before applying full power.

It is very unlikely you will cause any damage by trying it for a short time, watch, listen and smell ! If in doubt switch off quickly.

Be a sleuth

Boater Sam.

[reely reely]

When I mean dump them I meant put them back in the cupboard, sorry, my choice of words wernt really suitable, Im a hoarder sort of and doo hoard plus they arent mine they are me dads and I would never dump anything that looks remotely usefull unlike Dad who has disposed of certain audio and video equipment at the local tip in the past not thinking that one day they would be used again, so have no worries there, the valve is for project EL 3527 restore, a philips reel to reel machine which holds very strong memories for me from when I was a youngster, unfortunately its not our original as Dad dumped it but I do have all the tapes he made (60's pop music and sing something simple lol) which I treasure, and to play them again I thought why not on the exact same model of machine which I will restore to as best as possible.

Not being any good with valve id but with the advice given Ill do my best to identify the similar ones here, but also purchase another one just incase but can also use that to help find out whats here, I do like a challenge

[Herald1360]

Another heater quirk of the ECC81/2/3 series is that it's really a 12V series pair, with the centre tap on pin 9. So you should have roughly half the 4-5 resistance between 4-9 and 5-9.

Don't forget that 12AX7 is the US equivalent.

www.r-type.org has good pictures of valves for comparison purposes to try to separate -1 -2 -3 variants.

You won't blow anything up dropping a -1 or -2 type in by mistake and checking the electrode voltages should tell you if it's the right one or not.

Originally Posted by Boater Sam

Infra-red light will usually show up the original markings with luck, try the valves under a banknote checker.

I think Ultra Violet light might be more useful than just heating them up

[reely reely]

Looking at the pictures of a said ecc83, I have nothing in the box that matches, have one similar looking, an eb91 but obviously isnt equivalent in anyway, so one will have to be purchased Typical

[Herald1360]

Given the state of the market for these (Mullard) valves, go for some obscure manufacturer......

RS do one for £6.21 (+VAT +WHY)

[Tractorfan]

Hi,
If you can post some photos of the equipment and also the vacant valve holder, I'm sure our learned members could soon pin-point what the absentee is.
Also, have a look under the chassis. If heater pins 4&5 are connected together and the other side of the heater supply goes to pin 9, then it's almost certainly a ECC81/82/83.
Cheers, Pete.

[Herald1360]

Pete-

I don't think the identity of the valve required is the issue, just whether any of the OP's rummage box unmarked ones might do.

[reely reely]

Thx for the replies and help, not near the rummage box (do like that expression) just now but the closest looking one isn't compatible , it has a number on it which cross referenced is not the right valve, ill post some pics of the machine for interest when I can, have ordered a sh valve so hopefully it will work but there is a big possibility that there are other faults, time will tell lol.

[reely reely]

Here is a pic of all the excitement