[Amps] GM3SEK Tetrode and Triode Boards - updates
gm3sek at ifwtech.co.uk
Wed Jul 5 03:39:00 EDT 2017
It is very rare that the GM3SEK Triode Board and Tetrode Boards require
any announcements or updates... but here are a few today.
1. We're Back!
After some delays, the GM3SEK Triode Board and Tetrode Boards are back
in supply. Please order from the usual page,
2. Tetrode Boards - Technical Updates
(a) uA 748 availability
The uA748 op-amp IC used in the screen regulator is becoming obsolete
and there is no direct replacement. Fortunately I saw this coming, and
made a bulk buy so the Tetrode Boards can continue in production.
NEW: All future Tetrode Boards will be shipped with a uA748 IC at no
(The uA748 ICs in existing Tetrode Boards do not need to be replaced -
they're fine as they are.)
(b) Screen voltage stability
Newer uA748 ICs seem to have different gain from older samples, and in
some tube/transformer configurations this may cause a low-level
oscillation in the screen voltage regulator. If oscillation is suspected
or observed, then change C4 to 10nF. (The best way to check is with an
oscilloscope. Caution: always use a x10 'scope probe to measure G2
voltage. Also check the voltage rating of your probe.)
I am in process of updating the User Manual.
3. Fake Boards
WARNING - the "G3SEK Triode Boards" and "G3SEK Tetrode Boards" currently
for sale on eBay by Eastern European sellers like "9a3ru2008" and
"ham4ham2015" are FAKES!
I only provide help and technical support for my own boards.
4. Can You Help?
A customer in the USA needs some help in assembling and testing three
sets of Tetrode Boards (he has trouble with his eyesight). He can supply
all the components, and of course he will "make it worth your while" to
do the work. To avoid import/export complications, this work needs to be
done by someone in the USA.
If you think you can help, already have experience in building and
configuring the Tetrode Boards, and are in the USA, then please email me
at boards at ifwtech.co.uk
Final: Thanks to more than 2000 users of the *genuine* Triode and
Tetrode Boards for your continuing support.
73 from Ian GM3SEK
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