The "Sussex" Homebrew Valve Tester.

[Audioserve]

Originally Posted by G8UWM-MildMartin

I still have (28) PCBs for sale at cost (8.12 GBP).
Plus, maybe, the cost of a padded envelope, depending on whether any suitable used ones are being thrown away at work, plus the ever-increasing Royal Mail postage cost, minus the discount from using the franking machine at work, plus any applicable curency transfer or exchange fees.

Hi, Do you still have PCBs available?

[DIOMAR-BR]

Originally Posted by Audioserve

Hi, Do you still have PCBs available?

Hi, these pcbs are updated and new features added? You send to Brazil? Regards Diomar

[tritone]

Yes me too G8UWM-MildMartin, do you have any PCB's left for sale as I would love to build this tester. I sent you a PM.

Cheers.

[G8UWM-MildMartin]

PM replied to:
I had, last weekend, finally sold the last of the batch of 30 ordered from P&M Services 2 years ago.
I'll order some more to Mike Rowe's original design next week, unless anyone would like to announce or PM me this weekend/Monday about an improved version and/or being an alternative supplier. (Please!)
Thanks,
Martin.

[Ed_Dinning]

Hi Tritone, please clear your PM's, or e-mail me with your email address (via PM system), as I cannot reply to you as your PM box is full.
You have limited PM's allowed until you have more posts,.

Ed

[mikeydee]

Hi y'all. I have been away from this forum for a while.

I have been using my Sussex a lot recently. It has proved really useful for matching old valves and checking out what was wrong with some suspect ones.

One thing I wanted to share with the group was a problem of my own making. A while back my Sussex wasn't working with EL34 too (low readings) well although it had been with some other valves. We (mole42uk and a few others on the forum) were helping me debug on the principle that it was oscillations caused by wiring dress etc. So as part of that I had disconnected half of the sockets, added numerous ferrite beads and grid stoppers - all apparently giving very minor improvements.

So anyway the EL34 problem turned out to be something else, I seem to recall that it was an issue with the PCB layout or something but anyway I never removed any of my mods and found the Sussex fine with all the common guitar amp power valves but not with ECC83. One half would test fine and the second half nothing.

So I spent a long time checking all the wires working out what was going on and it must have been several sessions of this and many cups of tea before I found that one of my forgotten grid stoppers was actually in circuit on the heater supply only for the ECC83-B selection. So when you tested the ECC83-B, the heater voltage dropped very low over the stopper. I had not spotted it because I was concentrating on the anode, grid and cathode voltages.

What a dope! Such a pleasure to get it all working in the end though.

[G8UWM-MildMartin]

Latest batch of 15 PCBs from P&M Services have arrived. 3 reserved, remainder offered at cost: £9.68 plus £1.24 post (UK) giving a grand total of £10.92.

They are again to the Swordholder's (the late Mike Rowe's) original design, all on one platen with some excess, with the documented error in the HT supply, tinned, glass fibre, no silk-screened component ID, no solder resist and with all holes drilled 0.7-0.8mm.

My private email address is in "The Manual" by Keith or I can be contacted by PM here.

Martin.

[smbaker]

I have a question about the AC GM meter. I purchased a cheap 200mv AC meter from ebay. The problem is, it seems to be reading the DC component of the voltage across the 10 ohm resistor, so all it's doing is reading 10 times higher than the 200mv DC meter that's across the 1 ohm resistor.

Would it work to use AC coupling to my meter? For example, insert an 0.1uf capacitor on connection "A" between the 10 ohm resistor and the meter?

Thanks,
Scott

[mole42uk]

I would probably try to get a proper AC meter rather than starting out by modifying the circuit. The Sussex is a proven design these days and introducing another element before you've got the basic tester working might present difficulties. I know I had enough problems in the early days!

Can you let us know which meter you got? I know the ones most of us have used are cheap and reliable. The only problem with my AC meter is that the backlight goes out from time to time!

[vidjoman]

Make sure you have a fully isolated power supply for each meter. Separate transformer winding etc. There must not be any common connection between them.

[smbaker]

I'm using an isolated supply to each meter.

The meters I used were these ones: http://www.ebay.com/itm/140970861472...%3AMEBIDX%3AIT

Although an 'AC' meter, it's currently reading a negative voltage. /sigh

[mole42uk]

ISTR having trouble with my AC meter - I think the labels on the connectors were wrong.
I notice from the photos of yours that there is another voltage input position next to the connector - I wonder if this is the AC input?
Has the power supply enough current capability for an LED meter? Several of the Sussex's I know aboout use LCD displays which need a lower current, this isn't a definitive answer, I'm just curious.

[smbaker]

Unfortunately, the meter they shipped me isn't quite the same as the one in the picture in their listing. I'm not sure if it's older, newer, or just different. The one they shipped me has two screw terminals for power and two screw terminals marked something in Chinese. There aren't any additional pads that could be interpreted as another input.

It's stamped "5135A" on the back, but doing and image search doesn't show any other 5135A meters that look like it.

I've emailed the ebay seller for clarification, as I'm genuinely confused about this thing. I also went ahead and ordered a couple of the blue backlit LCD meters on ebay, in the hopes that I have better luck with those.

[Ed_Dinning]

The Sussex transformer is wound with 3 secondary's for meter power supplies, each giving a nominal 7V output. They are 22AWG insulated stranded wire so should should be capable of driving LED meters as well (assuming this is within the operating range of the LED meter).
Note that some of these meters have more than one "common" or "low" terminal that needs connecting as per that meter's instructions or it will not read accurately/ not have a good common mode rejection ratio.

Ed

[mole42uk]

Can you use a multimeter to measure the ac voltage at the terminals of the rogue Gm meter? That would at least prove that your Sussex was producing the correct output to the meter!

[smbaker]

I did. I had a 12AT7 under test, and my multimeter read about 5mV AC, which is what the AVO valve data manual told me to expect.

The AC DPM read -104mV. The DC DPM read 10.5mV.

[mole42uk]

Okay, it really sounds as though the AC meter is faulty. Can you get a refund from the ebay seller and buy another meter?

[smbaker]

I'm in communication with the seller, he wants pictures demonstrating the problem, which I will do. I do have two of the meters, and they both exhibit the same fault. Maybe someone is stuffing the wrong labels on them.

I do have some other meters on order from a different seller. So in another 3-4 weeks...

[paulsherwin]

No further discussion of the eBay transaction here please.

[mole42uk]

Sorry, Paul, I was just trying to help get another Sussex working reliably.