13-10-2016, 10:03 AM
How do you determine which valve holder the valve has to be plugged into?
Lawrence.
Lawrence.
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Avo Valve Tester
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13-10-2016, 11:46 AM
If you are referring to the test panel that came with it - I have no idea! Maybe it originally had a manual with the positions of various specific valves. For my first test, I put in a 4-pin triode, so there was not much chance of it connecting wrong.
If you mean my own test panel, that is simpilicty in itself, you put the valve in the socket that it fits. All the pin 1s are joined together and go to the red pin 1 socket along the top. Same with pin 2s etc. Marathon wiring job on the back, but it has served me well. Bob
13-10-2016, 11:51 AM
I enquired on UKVRR about the details of the unswitched panel but nothing is known schematic wise, I don't think that panel was in production for very long so you might have a rare one there.
Lawrence.
13-10-2016, 11:57 AM
http://golbornevintageradio.co.uk/forum/...p?tid=4877
I keep threatening to make another one for the 'Old' Valve Holders. Alan
13-10-2016, 12:02 PM
I don't suppose there is much to it. Checking with a continuity tester will soon show how it is wired. I will need to find out which are the top-cap connecters. But after I have my own panel up and running, I will probably dispose of the original valve-holder panel on Ebay - rare or not
 My sockets ordered yesterday, have just arrived, so I can now go ahead making up the new lead. Bob
15-10-2016, 02:56 PM
I have now done quite a lot of work on it. I cut three holes in the side, and inserted an octal socket, and two 4mm sockets. The 4mm sockets go to the LT supply. Seven of the pins in the Octal socket go to the corresponding pins on the original large 9-pin socket, the wiring of which has not been disturbed. A coupling box has also been made with and octal plug on one end of the lead (Old EF39 base). The 4mm sockets on the box are: Top row left to right: D1, D2 and A2. Bottom row, left to right: Cathode, Grid 1, Grid 2, Anode. I made up 6 jump leads with 4mm bananas on one end and 2mm bananas on the other. These join my home-made valve-holder panel to the Avo valve tester main unit. G3 can be linked to the cathode on the lower black terminals on my valve-holder panel. Initially, I found the filament volts too high. The mains setting was on 220V, so I moved it to 250V, and that corrected the filament volts. The anode and screen voltages are rather higher than those shown in the switch positions. As I am not able to select exact anode and screen voltages, I am not sure, at the moment, how accurate the test is! So far, everything I have tested is showing in the red. I will have to investigate further. Tracing the various connections on the 9-pin socket was a surprisingly tedious and long-drawn-out job.
Bob
16-10-2016, 02:10 PM
I use http://www.duncanamps.com/tdslpe/ which has an option to list valves by basing. If you select B7 there are dozens of different basings covering triodes, pentodes, beam tetrodes, rectifiers all with and without top caps. So the early unswitched version would only have been able to test a subset of available B7 valves.
Unfortunately the software does not seem to list B9 bases, but would expect to find the same thing regarding range of basings. Craig
16-10-2016, 02:50 PM
I have all the base connections in the valve data book thanks. The problem was tracing which pin on the 9-pin socket went to which electrode. Found them eventually, but it still does not work properly. For a start, the anode volatges are way out. Yesterday, I had an EF91 anode glowing white hot. When I put the meter on, the HT was in excess of 350 Volts on the 250V setting. I can get over that temporarily by going down two stops. But now, I find the one volt on the test switch is missing when I push it over. Possibly switch contacts, but bit difficult to get at.
Bob
16-10-2016, 03:05 PM
Some old design testers can sometimes break into oscillation when a more modern valve is inserted (high gm)
Lawrence.
Re: EF91.....According to the 11th edition of the Avo Valve Data Manual the anode switch setting for the EF91 is 100 volts and the screen switch setting is LF, there's a link to the manual below, it might take a while to upload.....Then scroll down to.......Test Data For Receiving And Small Transmitting Valves......The settings for the two panel tester are given in the columns headed.....AVT Data......The listings start with the OZ4 valve, the EF91 valve is listed on page 75 of that section.
It'll be worth saving that manual. Hope this helps. Lawrence. |
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