[GreenKeys] My Second Dovetron

[Paul Heller]

Fantastic update, Bill. You sure know what you’re doing. It was fun to read.

Paul
W2TTY

ITTY: 		HTTP://INTERNET-TTY.NET:8000/ITTY
ITTY100: 	HTTP://INTERNET-TTY.NET:8010/ITTY100
AUTOSTART: HTTP://INTERNET-TTY.NET:8030/AUTOSTART
EUROPE: 	HTTP://INTERNET-TTY.NET:8040/EUROPE

> On Jun 5, 2021, at 5:15 PM, William Wuttke <wcwuttke at att.net> wrote:
> 
> My first Dovetron is a bare-bones MPC-1000R Mk II S/N R770, black front & rear panels & case, early BBP-100 and
> no regenerator. It works pretty well after a few repairs.
> 
> I recently bought another MPC-1000R Mk II, S/N R032, but it has black front & side panels and blue rear panel, top, & 
> bottom, late model BBP-100, and a TSR-500 regenerator. (The rear panels of the two units are quite different from one another.
> 1. It arrived with the loop filter capacitor bottom lead broken at the capacitor - replaced.
> 2. I has a non-standard (old standard) 3 pin oval power connector which I broke when trying to make a workaround
> for the line cord. I bought a new connector, but was able to repair the original with a generous amount of epoxy.
> ( And I got the proper line cord.)
> 3. Next, I found that the loop current pot would not turn - the shaft was frozen - pulled apart and cleaned/lubricated.
> 4. The loop LED was burned out - replaced.
> 5. Had a couple of cold solder joints in the audio input circuit.
> 6. The AFSK monitor & switching functions of the BBP-100 were never enabled. Made a cable, installed 2 4066 ICs, but
> it didn't work - worked OK from the front panel SEND/RCV switch but not from the REMOTE connector using the +15V
> source on the back panel. The problem turned out to be that the 4.7K current limiting resistor for the +15V becomes
> part of a voltage divider with the rest of the SEND circuit which puts approx. 10 VDC on the control pins of the 4066.
> The 4066 requires 11VDC on the control pins. (It looks like the original 14066 was spec'd at 11 volts min., but typically
> triggered at 8.25VDC.) I put a 2.7K resistor in parallel with the 4.7K and resulted with 12+ volts at the control pins - Fixed!
> Now the cross-led display works both in receive and transmit - neat feature.
> 7. The AFSK switching function didn't work after getting the +15V sorted out. The problem was the switch on the BBP-100
> itself. Spring tension keeps contact spring fingers pressed up into the plastic handle assembly. I guess over the years, the
> spring tension just gave out. I bent the contact spring fingers a little, reassembled the switch, and all works again. (However,
> this is a function that I'll probably never use - I keep the AFSK output ON even during receive because it's easier to check
> my radio input level.) And, it doesn't really turn the AFSK all the way off during receive. The circuit parallels all 4
> CMOS switches to "ground" the AFSK signal during receive giving an approximate resistance of 30 ohms,
> which attenuates the signal a lot, but does not turn it off.
> 8. Modified the AFSK output circuit to give a variable, higher level output (did this on both units).
> 9. Made an "interface" to use RS-232 on the transmit side (TXD & RTS) using TLP222 solid state relays. It all fits inside
> a DE-9 backshell. On the first unit, I can use RS-232 transmit data, but, in order to use the regen capability on the second
> unit without modification, I need to use the loop for transmit data. RTS is only needed for the AFSK monitor. I key the
> transmitter with my computer interface program.
> 
> It was fun getting everything working correctly.....or at least to my satisfaction.
> 
> Now I can use it to transmit CQ and see my signals on RBN or WebSDRs or kiwiSDRs and maybe get lucky once in awhile
> to have someone respond to the CQ. Since the first of the year, I've only had RTTY QSOs with a handful of people.
> 
> Bill
> KE3BK
> ______________________________________________________________
> GreenKeys mailing list
> Home: http://mailman.qth.net/mailman/listinfo/greenkeys
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:GreenKeys at mailman.qth.net
> 
>>>> Jordan Spencer Cunningham's GreenKeys Search Tool: https://teletype.net/gksearch
>>>> 2002-to-present greenkeys archive: http://mailman.qth.net/pipermail/greenkeys/
>>>> 1998-to-2001 greenkeys archive: http://mailman.qth.net/archive/greenkeys/greenkeys.html
>>>> Randy Guttery's 2001-to-2009 GreenKeys Search Tool: http://comcents.com/tty/greenkeyssearch.html
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to phearvada at gmail.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/greenkeys/attachments/20210605/6dfc61a5/attachment.html>