Avo Valve Tester

[Sparks]

    It was like that when I got it, and it can't be brought to zero with the manual button.   But when it is switched on, it can be set to zero OK with the Set Zero knob!     I am now awaiting the small sockets for my new lead between my home-made valve-holder panel and the main unit.
    As a matter of interest, I phoned up the electronics firm to order the sockets, and was quoted eight pounds something for eight of them.      The postage was over £3, and I told them not to bother.     Off I went to Ebay, and quickly located the same sockets, paying £4.90 for 20 of them, and that included the postage.      Blow me down if it wasn't the same firm that wanted to prise over £8 off me for four of them!    
Bob  

[Mike Watterson]

Even Tesco and Argos are on eBay!

[Terry]

    It was like that when I got it, and it can't be brought to zero with the manual button.

Does the Zeroing screw move the pointer at all?

When you removed the movement, did you check that the pointer adjustment peg was correctly located inside the stirrup connected to the screw?

If all is OK in that area, can you see where the pointer has been bent and apply suitable restorative action?

[Sparks]

Yes, it does move it, but not enough. The pin is in the adjuster as it should be. As it can be zeroed by the zero adjust, I don't suppose it matters anyway. I may look into it further after I have satisfied myself that it is working OK. Not all that keen on taking the movement out, and I breathed a sign of relief after I had safely put it back again, but the loose glass made it necessary.
Bob

[pamphonica]

Sorry if I have missed something in this thread, but I am sure that this tester is missing a vital bit. You MUST have the standard Avo panel with the thumbwheel switches in order to test valves. This "add-on" valve base panel is then plugged into that panel. In the absence of that panel with thumbwheels you will need to do an awful lot of cross-patching of pins to get any sensible results.
Sorry if this is covered earlier but I have only had time to skim this thread.
Jeremy

[ppppenguin]

Jeremy, we may be wrong but see posts #9 and #10. Remember that this unit dates from a much simpler age before the multiplicity of pinouts that were found on later valves.

[pamphonica]

I see what you mean - how refreshingly simple. I am so conditioned to having to look up roller settings I had overlooked the obvious!
Jeremy

[pwdrive]

According to someone who's relative worked for AVO at that time, Avo were having problems with the design of the thumbwheel switch but they were under pressure to release a tester so it was released without the switch, this would tie up with the fact that the thumbwheel switch version was released within a year or two of the non switched version according to some old adverts I found on the web.

Lawrence.

[pwdrive]

In addition to Post#48, advert from 1939:

http://www.thevalvepage.com/testeq/avo/vt/advert.jpg

The new switched panel was called the Universal Panel, from reading the advert it's clear that it was also designed to replace the earlier unswitched panel.

Lawrence.

[Sparks]

         Following a long, and informative discussion on the telephone last night with   "Excessive Leakage," I am pleased to say that the Avo Valve tester is now fully functional!  
         Plug the valve in, and set the correct filament and anode volts etc.   Put "Select Anode" switch to "Normal" when testing triodes or pentodes.     "Set Zero" control fully clockwise and  "Set mA/V" control fully anti-clockwise.   Switch on.    Slowly work the "Set mA/V" control slowly up to the value from the valve data book for the valve under test, whilst maintaining the meter on zero by adjustment of the "Set Zero" control.     After this has been done, hold the "mA/V" switch to the left, and the valve's condition is shown.  
        As the valve-holder wiring is rather "dodgy," I have sent away for some flexible leads, sockets and plugs so that I can connect it to my home-made valve-holder panel.     In that way, I should be able to test a very wide range of valves.   I know some may find it a nuisance to have to deal with the jump leads rather than just select the valve via thumbwheels etc, but I really don't mind that.        
I am really delighted with this purchase, and the general construction, and engineering employed in making it is of the highest quality.     I lament very much the demise of the valve era, but am grateful that for the first 16 years of my career, when  transistors, and all that followed, were still in the future, and the valve still ruled supreme!
        Thanks for all your assistance, and advice.
Bob