Mullard Valve Tester - UK Vintage Radio Repair and Restoration Discussion Forum

Trev757 · 10th May 2005, 8:28 pm

Hi all

I am just about to put an old Mullard high speed valve tester on Ebay. However, not knowing how these operate, I don't want to mislead anyone in my description. Although the thing powers up, the valve heaters are alight and HT can be measured at various points around the circuit, there is no spot on the tube. Does this mean that it is faulty, or do you actually have to have a card and a valve plugged in before you get a spot? If the latter is the case, can someone give me the card number for a common valve and some brief operating instructions, in order that I can test further. I was going to put it on Ebay as non working, but would like to give as much info as possible.

My Taylor 45B is much easier!

thanks

Trev

Paul Stenning · 10th May 2005, 8:49 pm

Yes, it needs a card inserted for the spot to appear.

EL84 is card 635
EF86 is 561
6V6G is 270

The three relevant pages from the manual are attached. I think there is more abbreviated instructions on the test card index - I will check and scan it if there is.

Paul Stenning · 10th May 2005, 9:20 pm

Here's the abridged instructions from the card index. Sorry for the faint scan but the original is rather dirty so I had to tweak the threshold to make it readable!

high_vacuum_house · 10th May 2005, 9:42 pm

Hello there,
The Mullard valve tester has a safety switch built into the card reader which enables some contacts to close and the tester to operate only when a card is correctly inserted and seated.

If this safety switch was not present and a card was not inserted all of the contacts in the card reader matrix would close together causing many shorted turns on the mains transformer causing damage to it.

I had quite a few problems with mine when I bought it because the 6 pots under the front flap had been broken by someone putting too long screws to hold them in. Replacements cured the problem. I also replaced all of the old wax capacitors whilst I had it in bits.

Regards,
Christopher Capener

Trev757 · 10th May 2005, 10:24 pm

Paul

Many thanks for such a comprehensive reply and for taking the time to provide the attchments. I will have a play over the next couple of days and report back. Maybe I'll end up selling a working valve tester!

Christopher

Thanks for your input. I removed all the panels and found the big microswitch you refer to. That is working fine. Should I find that the tester works when I follow Paul's advise or if I can get it going without too much effort, then I'll certainly do all the routine tasks asociated with any restoration - including sending the wax paper capacitors to that great capacitor graveyard in the sky (and maybe some electrolytics as well!).

regards

Trevor

GMB · 11th May 2005, 2:34 pm

Before you test a valve you need to set the controls using the special calibration cards. These are labeled:

TEST MAINS
TEST HT
TEST REJECT

Trev757 · 11th May 2005, 3:59 pm

Following Paul's advise, I can now see a spot on the screen and adjust it's X position, focus and brilliance. The reject level and set zero controls do nothing and there is one labelled "don't touch" so I haven't touched! When testing a valve, heater volts and H.T can be measured at the socket. However, no matter where you put the test switch, or which button you press, the spot does not move on the screen. The test cards mentioned explain the one that was already in the machine when I got it. It is labelled mains and has just one hole in it. I will look for the others in the box, although I suspect these are for calibration purposes and I still should have seen the spot move when I tested a valve.

Oh dear, I was just going to sell this as a non worker; but I just can't resist having a dabble now. I should never have taken the bottom off and ventured inside in the first place!

Trev

GMB · 11th May 2005, 5:06 pm

I have images of the test cards if you need them - I needed these to identify the cards in my set since their tops had broken off through much use!

Trev757 · 11th May 2005, 6:07 pm

GMB

Many thanks for your kind offer. The cards I have are pretty good, it's mainly the white lettering at the top that is disappearing. However, I think there may be a couple of broken ones in there. I'll report back.

Trev757

Paul Stenning · 11th May 2005, 8:11 pm

I reckon replacing the wax-paper caps will get the unit working. These units are more sensitive to leaky caps than the average radio, so it doesn't take much leakage to stop it working. Mine had had the caps replaced previously with those metal-cased ones that look rather like electrolytics, but I still had to change the lot before it would behave properly. I used the yellow 1000V polyprop ones.

Incidently copies of the manuals etc are on my Valve Data CD-ROM.

10th May 2005, 8:28 pm	#1
Trev757 Banned Join Date: Dec 2004 Location: Bristol, UK. Posts: 218	Mullard Valve Tester Hi all I am just about to put an old Mullard high speed valve tester on Ebay. However, not knowing how these operate, I don't want to mislead anyone in my description. Although the thing powers up, the valve heaters are alight and HT can be measured at various points around the circuit, there is no spot on the tube. Does this mean that it is faulty, or do you actually have to have a card and a valve plugged in before you get a spot? If the latter is the case, can someone give me the card number for a common valve and some brief operating instructions, in order that I can test further. I was going to put it on Ebay as non working, but would like to give as much info as possible. My Taylor 45B is much easier! thanks Trev

10th May 2005, 9:20 pm	#3
Paul Stenning Administrator Join Date: Dec 2002 Location: Cardiff Posts: 9,072	Re: Mullard Valve Tester Here's the abridged instructions from the card index. Sorry for the faint scan but the original is rather dirty so I had to tweak the threshold to make it readable! Attached Thumbnails __________________ Paul Stenning Forum Admin/Owner and BVWS Webmaster

10th May 2005, 9:42 pm	#4
high_vacuum_house Octode Join Date: May 2003 Location: Belper Derbyshire Posts: 1,936	Re: Mullard Valve Tester Hello there, The Mullard valve tester has a safety switch built into the card reader which enables some contacts to close and the tester to operate only when a card is correctly inserted and seated. If this safety switch was not present and a card was not inserted all of the contacts in the card reader matrix would close together causing many shorted turns on the mains transformer causing damage to it. I had quite a few problems with mine when I bought it because the 6 pots under the front flap had been broken by someone putting too long screws to hold them in. Replacements cured the problem. I also replaced all of the old wax capacitors whilst I had it in bits. Regards, Christopher Capener __________________ Interests in the collection and restoration of Tefifon players and 405 line television

10th May 2005, 10:24 pm	#5
Trev757 Banned Join Date: Dec 2004 Location: Bristol, UK. Posts: 218	Re: Mullard Valve Tester Paul Many thanks for such a comprehensive reply and for taking the time to provide the attchments. I will have a play over the next couple of days and report back. Maybe I'll end up selling a working valve tester! Christopher Thanks for your input. I removed all the panels and found the big microswitch you refer to. That is working fine. Should I find that the tester works when I follow Paul's advise or if I can get it going without too much effort, then I'll certainly do all the routine tasks asociated with any restoration - including sending the wax paper capacitors to that great capacitor graveyard in the sky (and maybe some electrolytics as well!). regards Trevor

11th May 2005, 2:34 pm	#6
GMB Dekatron Join Date: Aug 2003 Location: near Reading (and sometimes Torquay) Posts: 3,097	Re: Mullard Valve Tester Before you test a valve you need to set the controls using the special calibration cards. These are labeled: TEST MAINS TEST HT TEST REJECT

11th May 2005, 3:59 pm	#7
Trev757 Banned Join Date: Dec 2004 Location: Bristol, UK. Posts: 218	Re: Mullard Valve Tester Following Paul's advise, I can now see a spot on the screen and adjust it's X position, focus and brilliance. The reject level and set zero controls do nothing and there is one labelled "don't touch" so I haven't touched! When testing a valve, heater volts and H.T can be measured at the socket. However, no matter where you put the test switch, or which button you press, the spot does not move on the screen. The test cards mentioned explain the one that was already in the machine when I got it. It is labelled mains and has just one hole in it. I will look for the others in the box, although I suspect these are for calibration purposes and I still should have seen the spot move when I tested a valve. Oh dear, I was just going to sell this as a non worker; but I just can't resist having a dabble now. I should never have taken the bottom off and ventured inside in the first place! Trev

11th May 2005, 5:06 pm	#8
GMB Dekatron Join Date: Aug 2003 Location: near Reading (and sometimes Torquay) Posts: 3,097	Re: Mullard Valve Tester I have images of the test cards if you need them - I needed these to identify the cards in my set since their tops had broken off through much use!

11th May 2005, 6:07 pm	#9
Trev757 Banned Join Date: Dec 2004 Location: Bristol, UK. Posts: 218	Re: Mullard Valve Tester GMB Many thanks for your kind offer. The cards I have are pretty good, it's mainly the white lettering at the top that is disappearing. However, I think there may be a couple of broken ones in there. I'll report back. Trev757

11th May 2005, 8:11 pm	#10
Paul Stenning Administrator Join Date: Dec 2002 Location: Cardiff Posts: 9,072	Re: Mullard Valve Tester I reckon replacing the wax-paper caps will get the unit working. These units are more sensitive to leaky caps than the average radio, so it doesn't take much leakage to stop it working. Mine had had the caps replaced previously with those metal-cased ones that look rather like electrolytics, but I still had to change the lot before it would behave properly. I used the yellow 1000V polyprop ones. Incidently copies of the manuals etc are on my Valve Data CD-ROM. __________________ Paul Stenning Forum Admin/Owner and BVWS Webmaster