A couple of weeks ago I bid on a Job lot (Bread-tray!) of items at a local auction and was fortunate to win them for £30, amongst the items was this tester of which I know nothing. The one thing I do know is that it looks like it's in a re-purposed AVO-8 Bakelite meter case!
I'm sure others will have them too, can anyone provide any information about it? I could do with a schematic or operating instructions if available.
Other items in the 'bread-tray' were a hallicrafters S-38 Radio, a 'Philco' thing which I've ascertained was some sort of intercom and also a quite neat but badly constructed home-made power supply.
The only things I've bothered with so far are the Pilot intercom and the PSU.
The intercom as been 'De-cased' as it was riddled with worm, the case is also in poor condition (drilled holes etc) so may be discarded. The circuit looks like a basic amplifier with changeover switch to use the speaker as a Mic. 4 Valves and a Barretter I think, looks like a large 'squirrel cage' lamp in a balloon envelope.
The PSU was poor, very poor. Some bad circuit design choices yet the PCB's looked to be very well made. Had some sort of 'traffic light' system of LED's on the front which appear to show current draw even though there is an Ammeter right there on the front panel. Based on the LM723, redesigned using the original Regulator PCB but removed the 'traffic light' system and installed a proper op-amp based current limiter.
Comments and Data are welcome.
Dave.
https://sites.google.com/site/davegsm82/projects/radioputer - A BC5441 Turned into a Media Centre PC.
Pictures....
https://sites.google.com/site/davegsm82/projects/radioputer - A BC5441 Turned into a Media Centre PC.
Is it just one of those strange things or is it true.
I looked at an old home made PSU that I bought about 30 years ago just the other day and thought even though one of the meters is missing the plastic cover perhaps I should fix it.
At the time I made a 723 one and it got neglected for all those years.
I did one that went down to zero volts from a reverse engineered ready made board with a couple of modifications.
Basically I made a negative rail with a pot to adjust it and transferred the low end of R1 and RV to it and replaced RI with a pot. I did not get perfect constant currant but it was not too far off. I have a feeling I also transferred R9 over too. It won't take much to do it again though.
I have a couple more of these boards and may well use a couple to make a proper power supply as I have a candidate for the transformer.
You can make it go to zero using an op- amp and connecting to the Comp pin. I can upload some pictures if you like?
I did have to generate a -ve line to add good current limiting, not necessary for 0 to 7 volts tho.
Dave.
https://sites.google.com/site/davegsm82/projects/radioputer - A BC5441 Turned into a Media Centre PC.
I have started to remember. It may have been all but the decoupling capacitors on the beefy power transformer that went to the negative line. The negative was no more than a shifted reference that had to be regulated as well as the main output needed to be.
The modified board had three more output transistors and R13s added and gave 10 amps 
It did have a fan and thermostat also added.
The one thing I do know is that it looks like it's in a re-purposed AVO-8 Bakelite meter case!
This was the final stage in meter design by Taylor before the Avo takeover, Avo seemed to use this design very quickly in their range.
