Guido Gay Memory (peak hold) Voltmeter MTA 1974 test teardown - Page 1
Forum section: electronics / testgear

author: oz2cpu
author_rank: Frequent Contributor
timestamp: July 26, 2025, 07:12:08 am
content: My latest score, this Amazing Peak storage hold voltmeter, from about 1974i scored this one real cheap at the last fleamarked,wow what a surprice to see its storage is ADC - DAC counter based.I removed an internal 6V Leadacid battery, and added IEC connector,I think this one is quite usefull for all sorts of experiments in my future, after i cleaned all switches it is now accurate and stable.picture and block schematics addedlink to a little video about this one :https://youtu.be/EajF0b_w8W8

author: Gyro
author_rank: Super Contributor
timestamp: July 26, 2025, 10:28:14 am
content: Nice video (as always). I enjoy the ones that cover stuff that I have!I'm not sure if mine is slightly earlier, the caps on the 'discrete' mains filter look slightly different. The original mains connector was an Italian style one. Luckily mine came with a mains lead.It is a neat design, Ing Guido Gay is a clever guy. He went on to do lots of deep sea exploration stuff - he has a Wikipedia page.The other difference is that yours has the isolated BNC. Mine came with a Lemo Triax socket, rather more expensive to connect to (it came with one lead but I needed to find another for my X10 attenuator. I'm not sure whether yours is original or retrofit.Yes, I constructed a X10 attenuator from scratch - I didn't like the input impedance being only 1Meg on the 1000V range! You can find a write up on it here...https://www.eevblog.com/forum/testgear/high-voltage-x10-attenuator-for-my-gay-mta-memory-voltmeter/The results seem pretty similar to those stated. 10Meg, <15pF (<20pF for the original). Note that the 10kV rating is dissipation limited, for transients only. The original could manage around 2.6kV continuous (0.7W dissipation), mine a little higher (although I haven't tested it for temperature rise in the plastic case, the resistors are very conservatively rated though). I don't use it above mains anyway.I'm just trying to think of other stuff. Oh yes, the SLA battery cooks and dries out if constantly powered from the mains. 7.5V is the cyclic charge voltage for a 6V battery, ok for quick recharge but not so good for mostly mains use. I replaced the Zener with a 6.8V (or 6.9V) one which gives roughly the standard float charge voltage. Note that there is no low battery warning if not running on mains, the Red LED simply fades out and you can forget to turn it off.I linked my post in the 'Show your Multimeter' thread in the above one, which shows internal and front panel views...https://www.eevblog.com/forum/chat/show-your-multimeter!/msg1426415/#msg1426415@Neomys Sapiens was kind enough to scan and post the manual for me, which I uploaded to KO4BB. Probably where you found it.In terms of use, it's very flexible. I normally use mine for monitoring mains spikes (with the attenuator), and general supply rails.I hope this helps.

author: oz2cpu
author_rank: Frequent Contributor
timestamp: July 27, 2025, 01:35:51 pm
content: WOW thanks for your reply Gyro,yes i found your pages and the scanned manual, good to mention them again,BIG thanks to all who scans and share,good idea with the hi voltage attenuator, i plan to look at it, since i do work with high voltage too