Racal Dana 9081 Problems - UK Vintage Radio Repair and Restoration Discussion Forum

g0hze snowy · 17th Oct 2013, 7:18 pm

Hi, a newbie to this site here,
I have been reading with interest the thread regarding the problems with the Racal 9081. I have 3 that are faulty, and have made some inroads by reading the replies to questions that others have had.
This has enabled me to partially recover one 9081, usual burnt exploded tants on 19-0846, now have the display, all zero's but that's better than nothing which is what I had.

My question/problem is when the x2-off-normal switch in the off position, I have a display. As soon as I move the switch lever to normal, no display and the power on LED goes off. I believe from reading the replies that it is the 12v rail going down, possibly again due to a s/c tant. Is that about right?, comments please.
Cheers Snowy

Moved from this thread: https://www.vintage-radio.net/forum/...580#post636580

PETERg0rsq · 17th Oct 2013, 10:39 pm

Yes

Exactly!!!!

Try C1 on Output board 19-0843, 22uF 16V tant.

Prime candidate for failing, and taking the 12V line down!

Regards

Peter

g0hze snowy · 18th Oct 2013, 8:00 am

Thanks Peter, as I am now semi retired and awaiting a visit to Papworth I have time to spend on these projects.

I am going out to the workshop so will try your suggestion, I will keep you posted.

Thanks, 73, Snowy.

tri-comp · 18th Oct 2013, 12:39 pm

If you think it will do you any good with a service-manual PM me with your e-mail address and I can help.

rgds,

/tri-comp

g0hze snowy · 18th Oct 2013, 2:33 pm

Hi Tri-comp
Many thanks for the offer, i do have a photo copy of the manual. I wouldn't have been able to repair 2 of the 3 i have without it and all the valuable help from members of this forum, so 2 down 1 to go, working on it now,cheers,Snowy

g0hze snowy · 18th Oct 2013, 2:38 pm

Hi Peter, many thanks for your help OM, that was exactly the beastie at fault,that one is now repaired and on long test at the moment, using the experience of you and other members, I have managed to resurrect another to working order.i then got big headed and started the 3rd one, again tant problems, then smoke from the tant (C5) on the spin wheel, sorted that but i have a frequency instability problem with it now, as another member said 3 steps forward 2 back. no change in frequency when i rotate the spin wheel, both leds are glowing, got to look further at this problem. cheers.Snowy

PETERg0rsq · 18th Oct 2013, 5:12 pm

Spin wheel problems are usually caused by some of the CMOS chips assosiated with it, plenty of helpful guidance in the manual, and easy to follow with a scope, or better still a storage scope!

If the frequency is drifting, then again I suspect the fault is with the frequency selection stages, either the spin wheel, or the up down switches> As there is a displayed frequency it shows the PLL is in lock, so it is responding to the divide by N part OK.

You will probably find some part of the tunning pulse generator circuit is oscillating, giving an output to the N counter. Could be the same fault as the spin wheel issue.

Start tracking the pulses at the encoder and trace them through the circuit and you should find the problkem easily enough.

Peter

g0hze snowy · 19th Oct 2013, 9:37 am

H Peter, well that was a disaster, 1 step forward and 3 back this time, have the same problem with the 19-0843 as before,have changed c1, that got it working but after a short while, 15mins or so, the display went down again, narrowed it down to same board, this time near the 4 x inductors,pin 32, if I remove the 12v supply from that point, display OK, if I link 12v feed wires together, still OK, so C1 side of the board OK, I have changed C117,looked hot, unable to find c123,220uF, have diagram but not sheet with component locations, is there one?.
Going to remove board for a better look, thanks to all for help so far.
cheers,Snowy

g0hze snowy · 19th Oct 2013, 10:51 am

Well thats a good mornings work, well till 10am anyway, changed C75, a s/c 22uF tant, i thought that would have exploded or burned but no just sat there,well i am back to showing a frequency on the display,changes with the selector switch but not locked, hopping around for a while then locks till you select up/down then goes off a random again, also the meter on FM/0M kicks to FSD, but ok on CW/AM, i think that is board 19-0843 POSS IC7?.
Cheers, Snowy

PETERg0rsq · 19th Oct 2013, 5:30 pm

Probably not IC7 on the output board, as this is used for CW (Carrier output power) and not for FM deviation.

You will need to look through the FM section to sort that out.

There are at least two FM variations that I am aware of!

The 9081 generates FM, then measures the FM deviation, and sends that to the meter. One variation uses an ALC system to keep the deviation constant, and the other variation relies on the user to control the FM deviation manualy as bands are switched.

I have complete manuals for both revisions, but you may find the one I uploaded to KO4BB is the correct one for you (it has the component layout for 19-0843)

Check out the Yahoo user group (if you can tolerate the mess Yahoo have made with it) Racal_Dana.

Peter

g0hze snowy · 19th Oct 2013, 9:42 pm

Peter, thanks for your patience, but i have had alot of success today, The frequency hopping was cured, after reading notes from others, by changing ic15 on the logic board, now i have a stable display, it is however slow to lock onto the chosen 'f', but it does settle and i now have a output tone, i listen to it on another 2m trx, by changing c13-c19,tl081 on the Audio board.
still dont have a meter indication on FM/0M and the mod level and the coarse control is critical when trying to use the pots, are they a possible problem?.
Do you know where i can locate a W300a FET
Once again thanks for all the help and advice.
Snowy

CambridgeWorks · 20th Oct 2013, 9:06 am

Hi Snowy.
There is a dil reed relay on the fm board that is a known problem. Cant remember if causes mod but no reading or vice versa.Also see my replies a year or two ago on 9081/2.
73. Robin

g0hze snowy · 20th Oct 2013, 2:09 pm

Hi All
Once again thanks to everybody re my problems with the 9081, i however being a clumsy t***t have now managed to snag and break the flexible coupling to the attenuator, all this as i am near to fixing the geni 100%, only problem i have now is eratic meter reading on FM, i have changed the FET W300A for a J310, the op amp tl081 and its associated tants, not giving them a second chance ha ha, Robin has suggested the reed relay, but, i dont have the circuit diagram for that board 19-0844, i have the component placings diagram, is there anybody out there that can email me it or supply another flexible coupling, payment isn't a problem.cheers, Snowy

g0hze snowy · 20th Oct 2013, 3:42 pm

SUCCESS!, well the meter is now moving as it should, board 19-0844 r24,c16,c65 + the 'c' in the 12v input rail, tants, what more can i say, just the attenuator coupling to get and replace, then i can confirm the attenuator is working as it should, then a 100% repair, i surprised myself, couldn't of done it with everybodies help tho'.cheers one and all.Snowy
P.S. dont forget a coupling if you have 1 lying around, fair price paid. thanks

CambridgeWorks · 20th Oct 2013, 9:50 pm

Hi Snowy, I cant remember exactly what the coupler looks like. Is it a bit thicker than the 0.25" shaft with 2 flex joints in it, made of plastic not metal? Poss about 1.5" to 2.5" long from memory? When fitted it is not quite inline, hence the flex.Can you let me know length overall that is required, how many "knuckles" and if it is fixed by 2 grub screws either end? I doubt I have an exact one......I THINK I can just about picture it! Let me know and I will see if I have an alternative.
The reed relay I referred to was used to disconnect the fm "mod meter" (deviation indicator circuit that drove meter) whilst rotating the flywheel. So it didn't knock itself senseless whilst tuning! Hence, a faulty relay would allow fm tone ok on carrier, but no mod indication on meter. AM was not affected.
Did you search out my other posts, some poss useful info there as well?
73, Robin

g0hze snowy · 21st Oct 2013, 8:10 am

Morning Robin, I will check out the dimensions that you ask for later today, got visitors soon, but your grey cell still working mate, more or less as you discribe, if i have you email address on my other pc i try to send a pic to you of it,it is secured by roll pin thru' the shaft of the attenuator so probably the same on the knob shaft.cheers,snowy

g0hze snowy · 21st Oct 2013, 8:17 am

Thanks for your help in resurrecting all 3 of my signal generators.
73
Snowy

g0hze snowy · 31st Oct 2013, 9:42 am

Good morning to all, well iI thought iI had done a complete repair on the 9081, but, when iI turning the frequency selection to 5-32megs, ( wanted to check sensitivity of a TEN TEC ARGONAUT 515) all iI got was zeroes, all other aspects of the geni are working.
Has anybody met this fault and its cure?
cheers
Snowy

PETERg0rsq · 31st Oct 2013, 10:40 pm

Are you saying that it is only the frequency display (counter) that is not working, or do you not have any output on range 1?

When no actual output from the 9081 you will get zeros in the display (just as when you turn the output off using the output switch).

Peter

g0hze snowy · 20th Jul 2014, 8:46 pm

Hi all, just a little more advice from you experts please, on one of the 9081's that iI have, Ii have removed it from my workbench with a view to selling it, on checking it over iI find that once again it has gone partially faulty on me.

1st fault is on the 5-32mhz range, no output, display is all zeroes except LED 3, that one is blank. Next problem is in the highest output postion, works fine up to 380MHz then the mod meter goes hard over to the right, mod pot has no effect.

What are the collective thoughts please?

Thanks, Snowy.

17th Oct 2013, 7:18 pm	#1
g0hze snowy Hexode Join Date: Oct 2013 Location: Peterborough, Cambridgeshire, UK. Posts: 336	Racal Dana 9081 Problems Hi, a newbie to this site here, I have been reading with interest the thread regarding the problems with the Racal 9081. I have 3 that are faulty, and have made some inroads by reading the replies to questions that others have had. This has enabled me to partially recover one 9081, usual burnt exploded tants on 19-0846, now have the display, all zero's but that's better than nothing which is what I had. My question/problem is when the x2-off-normal switch in the off position, I have a display. As soon as I move the switch lever to normal, no display and the power on LED goes off. I believe from reading the replies that it is the 12v rail going down, possibly again due to a s/c tant. Is that about right?, comments please. Cheers Snowy Moved from this thread: https://www.vintage-radio.net/forum/...580#post636580 Last edited by AC/HL; 17th Oct 2013 at 9:32 pm. Reason: Thread split

17th Oct 2013, 10:39 pm	#2
PETERg0rsq Heptode Join Date: Jun 2009 Location: St Helens, Lancashire, UK. Posts: 641	Re: Racal Dana 9081 Problems Yes Exactly!!!! Try C1 on Output board 19-0843, 22uF 16V tant. Prime candidate for failing, and taking the 12V line down! Regards Peter __________________ SPECIALIST.....Knows everything about nothing EXPERT..........Knows nothing about everything

18th Oct 2013, 8:00 am	#3
g0hze snowy Hexode Join Date: Oct 2013 Location: Peterborough, Cambridgeshire, UK. Posts: 336	Re: Racal Dana 9081 Problems Thanks Peter, as I am now semi retired and awaiting a visit to Papworth I have time to spend on these projects. I am going out to the workshop so will try your suggestion, I will keep you posted. Thanks, 73, Snowy.

18th Oct 2013, 12:39 pm	#4
tri-comp Heptode Join Date: Oct 2008 Location: Aalborg, Denmark Posts: 903	Re: Racal Dana 9081 Problems If you think it will do you any good with a service-manual PM me with your e-mail address and I can help. rgds, /tri-comp

18th Oct 2013, 2:33 pm	#5
g0hze snowy Hexode Join Date: Oct 2013 Location: Peterborough, Cambridgeshire, UK. Posts: 336	Re: Racal Dana 9081 Problems Hi Tri-comp Many thanks for the offer, i do have a photo copy of the manual. I wouldn't have been able to repair 2 of the 3 i have without it and all the valuable help from members of this forum, so 2 down 1 to go, working on it now,cheers,Snowy

18th Oct 2013, 2:38 pm	#6
g0hze snowy Hexode Join Date: Oct 2013 Location: Peterborough, Cambridgeshire, UK. Posts: 336	Re: Racal Dana 9081 Problems Hi Peter, many thanks for your help OM, that was exactly the beastie at fault,that one is now repaired and on long test at the moment, using the experience of you and other members, I have managed to resurrect another to working order.i then got big headed and started the 3rd one, again tant problems, then smoke from the tant (C5) on the spin wheel, sorted that but i have a frequency instability problem with it now, as another member said 3 steps forward 2 back. no change in frequency when i rotate the spin wheel, both leds are glowing, got to look further at this problem. cheers.Snowy

18th Oct 2013, 5:12 pm	#7
PETERg0rsq Heptode Join Date: Jun 2009 Location: St Helens, Lancashire, UK. Posts: 641	Re: Racal Dana 9081 Problems Spin wheel problems are usually caused by some of the CMOS chips assosiated with it, plenty of helpful guidance in the manual, and easy to follow with a scope, or better still a storage scope! If the frequency is drifting, then again I suspect the fault is with the frequency selection stages, either the spin wheel, or the up down switches> As there is a displayed frequency it shows the PLL is in lock, so it is responding to the divide by N part OK. You will probably find some part of the tunning pulse generator circuit is oscillating, giving an output to the N counter. Could be the same fault as the spin wheel issue. Start tracking the pulses at the encoder and trace them through the circuit and you should find the problkem easily enough. Peter __________________ SPECIALIST.....Knows everything about nothing EXPERT..........Knows nothing about everything

19th Oct 2013, 9:37 am	#8
g0hze snowy Hexode Join Date: Oct 2013 Location: Peterborough, Cambridgeshire, UK. Posts: 336	Re: Racal Dana 9081 Problems H Peter, well that was a disaster, 1 step forward and 3 back this time, have the same problem with the 19-0843 as before,have changed c1, that got it working but after a short while, 15mins or so, the display went down again, narrowed it down to same board, this time near the 4 x inductors,pin 32, if I remove the 12v supply from that point, display OK, if I link 12v feed wires together, still OK, so C1 side of the board OK, I have changed C117,looked hot, unable to find c123,220uF, have diagram but not sheet with component locations, is there one?. Going to remove board for a better look, thanks to all for help so far. cheers,Snowy

19th Oct 2013, 10:51 am	#9
g0hze snowy Hexode Join Date: Oct 2013 Location: Peterborough, Cambridgeshire, UK. Posts: 336	Re: Racal Dana 9081 Problems Well thats a good mornings work, well till 10am anyway, changed C75, a s/c 22uF tant, i thought that would have exploded or burned but no just sat there,well i am back to showing a frequency on the display,changes with the selector switch but not locked, hopping around for a while then locks till you select up/down then goes off a random again, also the meter on FM/0M kicks to FSD, but ok on CW/AM, i think that is board 19-0843 POSS IC7?. Cheers, Snowy

19th Oct 2013, 5:30 pm	#10
PETERg0rsq Heptode Join Date: Jun 2009 Location: St Helens, Lancashire, UK. Posts: 641	Re: Racal Dana 9081 Problems Probably not IC7 on the output board, as this is used for CW (Carrier output power) and not for FM deviation. You will need to look through the FM section to sort that out. There are at least two FM variations that I am aware of! The 9081 generates FM, then measures the FM deviation, and sends that to the meter. One variation uses an ALC system to keep the deviation constant, and the other variation relies on the user to control the FM deviation manualy as bands are switched. I have complete manuals for both revisions, but you may find the one I uploaded to KO4BB is the correct one for you (it has the component layout for 19-0843) Check out the Yahoo user group (if you can tolerate the mess Yahoo have made with it) Racal_Dana. Peter __________________ SPECIALIST.....Knows everything about nothing EXPERT..........Knows nothing about everything

19th Oct 2013, 9:42 pm	#11
g0hze snowy Hexode Join Date: Oct 2013 Location: Peterborough, Cambridgeshire, UK. Posts: 336	Re: Racal Dana 9081 Problems Peter, thanks for your patience, but i have had alot of success today, The frequency hopping was cured, after reading notes from others, by changing ic15 on the logic board, now i have a stable display, it is however slow to lock onto the chosen 'f', but it does settle and i now have a output tone, i listen to it on another 2m trx, by changing c13-c19,tl081 on the Audio board. still dont have a meter indication on FM/0M and the mod level and the coarse control is critical when trying to use the pots, are they a possible problem?. Do you know where i can locate a W300a FET Once again thanks for all the help and advice. Snowy

20th Oct 2013, 9:06 am	#12
CambridgeWorks Nonode Join Date: Jun 2010 Location: Spalding, Peterborough, Cambridgeshire, UK. Posts: 2,859	Re: Racal Dana 9081 Problems Hi Snowy. There is a dil reed relay on the fm board that is a known problem. Cant remember if causes mod but no reading or vice versa.Also see my replies a year or two ago on 9081/2. 73. Robin

20th Oct 2013, 2:09 pm	#13
g0hze snowy Hexode Join Date: Oct 2013 Location: Peterborough, Cambridgeshire, UK. Posts: 336	Re: Racal Dana 9081 Problems Hi All Once again thanks to everybody re my problems with the 9081, i however being a clumsy t***t have now managed to snag and break the flexible coupling to the attenuator, all this as i am near to fixing the geni 100%, only problem i have now is eratic meter reading on FM, i have changed the FET W300A for a J310, the op amp tl081 and its associated tants, not giving them a second chance ha ha, Robin has suggested the reed relay, but, i dont have the circuit diagram for that board 19-0844, i have the component placings diagram, is there anybody out there that can email me it or supply another flexible coupling, payment isn't a problem.cheers, Snowy

20th Oct 2013, 3:42 pm	#14
g0hze snowy Hexode Join Date: Oct 2013 Location: Peterborough, Cambridgeshire, UK. Posts: 336	Re: Racal Dana 9081 Problems SUCCESS!, well the meter is now moving as it should, board 19-0844 r24,c16,c65 + the 'c' in the 12v input rail, tants, what more can i say, just the attenuator coupling to get and replace, then i can confirm the attenuator is working as it should, then a 100% repair, i surprised myself, couldn't of done it with everybodies help tho'.cheers one and all.Snowy P.S. dont forget a coupling if you have 1 lying around, fair price paid. thanks

20th Oct 2013, 9:50 pm	#15
CambridgeWorks Nonode Join Date: Jun 2010 Location: Spalding, Peterborough, Cambridgeshire, UK. Posts: 2,859	Re: Racal Dana 9081 Problems Hi Snowy, I cant remember exactly what the coupler looks like. Is it a bit thicker than the 0.25" shaft with 2 flex joints in it, made of plastic not metal? Poss about 1.5" to 2.5" long from memory? When fitted it is not quite inline, hence the flex.Can you let me know length overall that is required, how many "knuckles" and if it is fixed by 2 grub screws either end? I doubt I have an exact one......I THINK I can just about picture it! Let me know and I will see if I have an alternative. The reed relay I referred to was used to disconnect the fm "mod meter" (deviation indicator circuit that drove meter) whilst rotating the flywheel. So it didn't knock itself senseless whilst tuning! Hence, a faulty relay would allow fm tone ok on carrier, but no mod indication on meter. AM was not affected. Did you search out my other posts, some poss useful info there as well? 73, Robin

21st Oct 2013, 8:10 am	#16
g0hze snowy Hexode Join Date: Oct 2013 Location: Peterborough, Cambridgeshire, UK. Posts: 336	Re: Racal Dana 9081 Problems Morning Robin, I will check out the dimensions that you ask for later today, got visitors soon, but your grey cell still working mate, more or less as you discribe, if i have you email address on my other pc i try to send a pic to you of it,it is secured by roll pin thru' the shaft of the attenuator so probably the same on the knob shaft.cheers,snowy

21st Oct 2013, 8:17 am	#17
g0hze snowy Hexode Join Date: Oct 2013 Location: Peterborough, Cambridgeshire, UK. Posts: 336	Re: Racal Dana 9081 Problems Thanks for your help in resurrecting all 3 of my signal generators. 73 Snowy Last edited by AC/HL; 21st Oct 2013 at 3:19 pm. Reason: Email removed

31st Oct 2013, 9:42 am	#18
g0hze snowy Hexode Join Date: Oct 2013 Location: Peterborough, Cambridgeshire, UK. Posts: 336	Re: Racal Dana 9081 Problems Good morning to all, well iI thought iI had done a complete repair on the 9081, but, when iI turning the frequency selection to 5-32megs, ( wanted to check sensitivity of a TEN TEC ARGONAUT 515) all iI got was zeroes, all other aspects of the geni are working. Has anybody met this fault and its cure? cheers Snowy

31st Oct 2013, 10:40 pm	#19
PETERg0rsq Heptode Join Date: Jun 2009 Location: St Helens, Lancashire, UK. Posts: 641	Re: Racal Dana 9081 Problems Are you saying that it is only the frequency display (counter) that is not working, or do you not have any output on range 1? When no actual output from the 9081 you will get zeros in the display (just as when you turn the output off using the output switch). Peter __________________ SPECIALIST.....Knows everything about nothing EXPERT..........Knows nothing about everything

20th Jul 2014, 8:46 pm	#20
g0hze snowy Hexode Join Date: Oct 2013 Location: Peterborough, Cambridgeshire, UK. Posts: 336	Re: Racal Dana 9081 Problems Hi all, just a little more advice from you experts please, on one of the 9081's that iI have, Ii have removed it from my workbench with a view to selling it, on checking it over iI find that once again it has gone partially faulty on me. 1st fault is on the 5-32mhz range, no output, display is all zeroes except LED 3, that one is blank. Next problem is in the highest output postion, works fine up to 380MHz then the mod meter goes hard over to the right, mod pot has no effect. What are the collective thoughts please? Thanks, Snowy.