Re: Racal RA-6790GM/R2174 New to Me
Guys, I just did up a Cubic R3080 last winter changing out all the power bus caps that has the same disease. New tantalum caps are just as bad as the old ones so I decided to replace all the 10uF power bus caps with 1uF /100V Kemet ceramic caps I bought from Mouser. Good price break when you buy a bag of 100. The power bus bypass cap value is not critical. Everything worked fine when I am done. I think it was over 60 caps but the ceramic caps will out last me.? While working our company decided to stop using tantalum caps. It wasn't worth the time we were spending on failure reports and unhappy customers. Frank WA1GFZ
On Saturday, November 30, 2024 at 11:10:33 AM EST, Dan Rae via groups.io <danrae@...> wrote:
Peter, I will make one well intentioned criticism of your advice,
which was to use a NiCad battery, leakage from which has destroyed
a lot of A6A2 cards.? Use instead a NiMH replacement which are
much prone to leakage.? One used to be able to get a Varda
"Mempac" German made battery that was a direct drop in replacement
for the original.? If that can't be got any more a little daughter
card can be made to fit whatever is available.? I have used many
of these Vardas over the years with excellent results.? Looking at
my remaining stock recently showed they still have charge!
I agree with the use of LEDs for edge lighting using the original
boards, but a more even result can be got with four series
connected strings of seven sideways firing LEDs with one series
100 Ohm R in each string.? Three wire links are needed, with slots
cut in the existing traces for the LEDs, see attached pic.
Assuming there has been battery leakage in the past with the
original poster's CPU, the A6A2 board would have to be cleaned and
examined very closely,? The leakage is alkaline and can be
neutralised with some dilute vinegar followed by washing with
isopropyl alcohol.? That nasty stuff gets everywhere with a
fondness for destroying VIAs, creeping up transistor and IC leads
and dissolving the copper inside the plastic body, getting into
the 34 way connector next to the battery.? Any signs of dull grey
solder or traces of blue near anything copper are bad news.
A6A2 boards can be fixed if not too badly damaged, also
new replacement boards are available.
73 - Dan
ac6ao / g3ncr
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Re: Racal RA-6790GM/R2174 New to Me
Peter, I will make one well intentioned criticism of your advice,
which was to use a NiCad battery, leakage from which has destroyed
a lot of A6A2 cards.? Use instead a NiMH replacement which are
much prone to leakage.? One used to be able to get a Varda
"Mempac" German made battery that was a direct drop in replacement
for the original.? If that can't be got any more a little daughter
card can be made to fit whatever is available.? I have used many
of these Vardas over the years with excellent results.? Looking at
my remaining stock recently showed they still have charge!
I agree with the use of LEDs for edge lighting using the original
boards, but a more even result can be got with four series
connected strings of seven sideways firing LEDs with one series
100 Ohm R in each string.? Three wire links are needed, with slots
cut in the existing traces for the LEDs, see attached pic.
Assuming there has been battery leakage in the past with the
original poster's CPU, the A6A2 board would have to be cleaned and
examined very closely,? The leakage is alkaline and can be
neutralised with some dilute vinegar followed by washing with
isopropyl alcohol.? That nasty stuff gets everywhere with a
fondness for destroying VIAs, creeping up transistor and IC leads
and dissolving the copper inside the plastic body, getting into
the 34 way connector next to the battery.? Any signs of dull grey
solder or traces of blue near anything copper are bad news.
A6A2 boards can be fixed if not too badly damaged, also
new replacement boards are available.
73 - Dan
ac6ao / g3ncr
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Re: Racal RA-6790GM/R2174 New to Me
Hi Peter, ? Thank you for the suggestions. I have a couple hours today to work on it. So far found two open traces on the A6A2 board, repaired them but still have issues. I tested all of the traces as well as their connections to the front panel ¨C everything seems intact now. ? I have a feeling that the A6A2 board will be replaced soon¡¡¡ ? What serial number is your radio? Mine is 3265 on the Racal ID plate and 3198 on the R-2174 ID plate. ? Tom W3TA ?
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From: [email protected] < [email protected]> On Behalf Of Peter E via groups.io Sent: Friday, November 29, 2024 10:14 PM To: [email protected]Subject: Re: [RacalRadio] Racal RA-6790GM/R2174 New to Me ? I have just finished repairing an RA6790 and its a very nice receiver when its going! I am no kind of expert on these but I can answer some of your questions. The battery in mine (and I assume yours) should be 2.4V. Just replace it with any NiCad battery pack with that voltage - many cordless phones have similar batteries, and you can just velcro it to the side of the case somewhere. Mine exhibited all sorts of strange behaviour till I replaced it - would start doing a BITE test then hang at some point. The bulbs on my display were all burnt out - I have now replaced all of the bulbs with green SMD LED's and 4K7 resistors - see photo attached. Two of the tantalums were shorted in mine - in the First mixer (A2) and had taken out a choke as well. I am not normally a fan of shotgun cap replacement but am now tossing up whether to replace all the rest - thoughts anyone? I noted that they were 20V tantalums running at 16V - not enough safety margin I would suggest.? The three transistors in A2 seem to run VERY hot! I added some additional heatsinking - not sure if its necessary but cant hurt. Yours sounds like it may have issues with the A6A2 board. replcae the battery first then go from there I would suggest. Hopefully you proms are not damaged.
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Re: Racal RA-6790GM/R2174 New to Me
Hi Tom,
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I have just finished repairing an RA6790 and its a very nice receiver when its going!
I am no kind of expert on these but I can answer some of your questions. The battery in mine (and I assume yours) should be 2.4V. Just replace it with any NiCad battery pack with that voltage - many cordless phones have similar batteries, and you can just velcro it to the side of the case somewhere. Mine exhibited all sorts of strange behaviour till I replaced it - would start doing a BITE test then hang at some point.
?
The bulbs on my display were all burnt out - I have now replaced all of the bulbs with green SMD LED's and 4K7 resistors - see photo attached.
?
Two of the tantalums were shorted in mine - in the First mixer (A2) and had taken out a choke as well. I am not normally a fan of shotgun cap replacement but am now tossing up whether to replace all the rest - thoughts anyone? I noted that they were 20V tantalums running at 16V - not enough safety margin I would suggest.?
?
The three transistors in A2 seem to run VERY hot! I added some additional heatsinking - not sure if its necessary but cant hurt.
?
Yours sounds like it may have issues with the A6A2 board. replcae the battery first then go from there I would suggest. Hopefully you proms are not damaged.
?
Cheers, and good luck!
Peter - VK2AN
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I was lucky enough to be given an RA1779 the other day. When I turn it on all I get is a loud hum and error message, so I assume the power supply may be suspect.
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Does anyone know where I might be able to find a manual for this receiver??
?
Cheers,
Peter - VK2AN
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Re: F/S SINCAL 2000 VIU RAILS
HI Richard,
No problem
Jeff
On 27/11/2024 15:42 GMT Richard G7RVH via groups.io <badwolf1959@...> wrote:
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Jeff,
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I have replied direct via this group and via email. I've tried a few times so no idea what is happening. Perhaps I am being dumped as spam.
?
Can I use the mobile number that ends in '030' to contact you?
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Or you can email me via the details on QRZ and hopefully that will work.
?
Richard
?
G7RVH
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Racal RA-6790GM/R2174 New to Me
One of these radios found a home at my house yesterday. I am typically a collector / restorer of tube based radios, but have had a couple Harris RF-590's and a Watkins Johnson. I am familiar with digital circuits (I've been in the electronics engineering field most of my career) and know my way around an O'Scope.
I have directly emailed Gary the following but thought I'd post to the group as well.
1. Radio is populated with "VLF" Eproms and an assortment of filters.?
1a. Battery was changed (now dead) says 3.6v but manual says 2.4v. What should I replace it with?
2. The radio powers up, voltages at the power supply are good, but there is no front panel response. Small LCD shows two digits in upper right corner, Freq LCD shows random numbers that don't change, but can be different after power cycle.
3. The three OOL LEDs are lit on the A9 card - obviously pointing me to some phase lock issues.
4. There is 15v at the LCD lamps but they are not on. I can't imagine they are all bad. Unpowered there is 100 ohms across the lamp circuit so seems like some / most filaments are intact.
5. The Silver backing of the LCDs is discolored - are replacements available?
6. Where is a good source for spare parts?
7. I expect I'll have to go through and replace many, if not all, of the tantalums like I had to do on the Harris radios I had.
I just got the radio yesterday and did a quick survey of condition last night. Hope to find time to dig further this weekend. I have downloaded the operating and service manuals as well.
Any direction is appreciated.
Tom? W3TA
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Re: F/S SINCAL 2000 VIU RAILS
Jeff,
?
I have replied direct via this group and via email. I've tried a few times so no idea what is happening. Perhaps I am being dumped as spam.
?
Can I use the mobile number that ends in '030' to contact you?
?
Or you can email me via the details on QRZ and hopefully that will work.
?
Richard
?
G7RVH
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Re: F/S SINCAL 2000 VIU RAILS
HI RIchard.
No i've not heard anything from you since i asked you to contact me direct.
?
Jeff
G8XXI
On 27/11/2024 10:49 GMT Richard G7RVH via groups.io <badwolf1959@...> wrote:
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Jeff,
?
Did you receive the email with my contact details?
?
I am still very interested in acquiring a set of these rails.
?
Richard
G7RVH
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eprom hex-bin files ra1792
Are there members who can help me with hex eprom files
for a racal ra1792? I am looking for versions that have the 1Hz readout and
?when possible with the ieee488 gpib interface .
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Re: F/S SINCAL 2000 VIU RAILS
Jeff,
?
Did you receive the email with my contact details?
?
I am still very interested in acquiring a set of these rails.
?
Richard
G7RVH
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I run a 6790GM and it shares input through a Racal antenna tuner that front end bandwidth limits to a 1 MHz slice of HF bandwidth, determined by slave to a RA 6217E.
This feeds a 8 port Nuvistor multicoupler that adds 7db gain in a rural location. This transformed the receiver IMHO. I run the 455 out to a Sherwood SE3 to make audio easier, however the synchronous detection of the receiver is flawless.
The 6217E is greatly benefited by the SE-3, in fact, there is no question that it is the top receiver here, and my Sherwood modded Drake R-4C noise floor is black ink.
My .02 cents worth.
On Sat., Nov. 23, 2024, 9:48 a.m. Kees PE7ST via , <forum444= [email protected]> wrote: Yes that is true. But surely the specs like dynamic range and blocking still give useful information on the front end of the receiver?
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73
Kees
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Yes that is true. But surely the specs like dynamic range and blocking still give useful information on the front end of the receiver?
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73
Kees
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are there members who can help me with hex eprom files
for a racal ra1792? I am looking for versions that have the 1Hz readout and
also have the ieee488 gpib interface .
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Bezel [Escutcheon] for Racal RA117 etc.
I am restoring a Racal RA117? that came into my hands having no black Bakerlite bezel. I`m hoping that someone on this group can help me get one to make this
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Re: Racal BCC 540G AAMTU Question
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Dave,
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Many thanks for your clear and informative response. I now understand what is going on with the Syncal 2000 / VIU / 540G combination that I have.
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Also, the information regarding the other C & F variants is equally useful.
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Richard
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G7RVH
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Re: Racal BCC 540G AAMTU Question
Hi Richard
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The momentary break method does not store any data, each time it is initiated it resets the microprocessor and completes an active tune cycle with RF to match the antenna as best it can.
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When a PWM data word is sent from a suitable radio the BCC540G checks to see if it already has it in memory, if not it it completes an active tune cycle with RF to match the antenna as best it can.
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If the 8 bit PWM data word is in memory it checks the first bit which will either initiate an active tune with RF by recalling the capacitor and inductor settings stored in one of the 128 memories or indicate a passive tune (silent tune no RF) by recalling from one of the 128 memories the relay settings for capacitors and inductors.
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The memory which holds the capacitor and inductor relay settings is RAM which is held up by the battery so that information remains stored.
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When DC power is removed from the unit the relays and CPU reset so the current tune status is lost and tuning will need to be reinitiated on power on with either an active tune or passive tune described above.
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This is also the case for the BCC540C and BCC540F
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Regards
Dave g1jwg
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Re: Racal BCC 540G AAMTU Question
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Dave,
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Thanks for your response.
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Just to be clear when using the momentary break method no data is stored. Tuning data is only stored when using the PWM method. Is this data still stored when the unit has no supply e.g. when the connected radio is powered off?
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Richard
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G7RVH
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Re: Programmer MA4073C EMU
Graham,? I dont use groups.io so much, so I ask a stupid question. How can I use graham_douglas@.... ?
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Peter E
Richard G7RVH