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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment. |
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24th Apr 2010, 3:12 pm | #1 |
Retired Dormant Member
Join Date: May 2007
Location: Exeter, Devon, UK.
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RA17W where to start
Hi all
Ive just finished my AR88D Now Its time to have ago at my Racal Ra17w Is there anything I should look out for before I power it up. Plus Its full of hunts metallished paper capacitors, so would it be best to replace these on sight. Just downloaded service a manual and removed covers so far Cheers Pete |
24th Apr 2010, 11:54 pm | #2 |
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Re: RA17W where to start
My B40C, which predates your RA17, is riddled with metalised paper capacitors.
As far as I can tell, they all work beautifully Alan |
25th Apr 2010, 12:06 am | #3 |
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Re: RA17W where to start
Hi Pete,
I have the RA17L, never had any probs with the capacitors, although if you find you have low signal strengths the anode and screen bypass caps are often suspect, especially in the RF and demodulator/AGC areas. Have you had any re-alignment probs with your AR88D ? I read up on it and it seems a bit of a challenge ( mine is still on the bench with low sinals on one band only..the others are dead. Mike. |
25th Apr 2010, 12:39 pm | #4 |
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Re: RA17W where to start
Please start a new thread regarding AR88 alignment. This one is about RA17Ls
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26th Apr 2010, 11:37 am | #5 |
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Re: RA17W where to start
Start with the mains lead and connections. Make sure it's properly wired and fused and and the case is earthed.
Next eyeball the whole set for replaced components and bodges. Look for anything obviously burned. If you find anything odd, investigate. Check the main smoothing cap for a bulging vent and reform it. The smoothing cap is hard to get at. Check that the crystal is a 1MHz one. It probably is, but if you assume that and it isn't, it's a phenomenal waste of time. Power the set up gently through a lamp limiter and check that the voltages are what you expect. Make sure the audio section works. When that works, go to the IF section and set it up as per the instructions. The caps don't seem to cause many problems. You'll almost certainly find a lot of resistors which have gone O/C or hopelessly high. According to this http://www.recelectronics.demon.co.uk/ra17.htm The RA17W is a minor variant of the RA17L with different IF bandwidths. As for mechanical problems, an obvious one is the film scale roller. It tends to stick and a flat wears on the roller. This is not good for the film scale and not the way it should be. You haven't got much option but to press the roller and bearings out and get a replacement roller machined up. If the bearings are rusted and grotty and don't respond to good clean and lubrication, they are probably standard parts. If you are in luck you'll see the roller turn easily with the slightest movement of the film scale and the roller will show no signs of flats. Pete. |
26th Apr 2010, 6:49 pm | #6 |
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Re: RA17W where to start
Hi
Thank you all for the advice/tips now its sat on me bench with a few more resistors to check Then hopefully ready for the big switch on this weekend so fingers crossed Cheers pete |
8th Jun 2010, 4:53 pm | #7 |
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Re: RA17W where to start
Hi All
What a nightmare of a project maybe bit off more than i can chew I have now got the output stage working now Both 1st/2nd VFOs and IF had high/burnt out resistors etc so no more smoke V24 replaced cv464 but still can not pick up anything but hash noise any ideas where to go from here Please Cheers pete |
8th Jun 2010, 7:08 pm | #8 |
Hexode
Join Date: Apr 2003
Location: Cotswolds, UK.
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Re: RA17W where to start
What do you have in the way of test gear? You won't be able to do this without a decent signal generator and one of the filter chains needs a good wobbulator. I haven't got the manual to hand but in essence work through backwards from the AF to the RF.
If you get stuck I'll dig the manual out but there are many people on this site who have been down this path who can help. Robin |
8th Jun 2010, 7:29 pm | #9 | |
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Re: RA17W where to start
Quote:
Al. / Skywave. |
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14th Jun 2010, 9:35 am | #10 |
Tetrode
Join Date: Dec 2007
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Re: RA17W where to start
Greetings to all.
If anyone seriously believes they can restore any RA17 variant to correct working order WITHOUT replacing the dreaded Hunts paper capacitors then they are dreamers of the first order! Measure the leakage current of any of these dreadful things with 350Volts applied and you will soon see what I mean.Sure,you can have leaky cathode bypass capacitors but these will continue to fall below acceptable limits. Don't fool yourseleves,replace all these monsters,after all,how many times do you want to dismantle a 17,especially the firt and second VFOs? Brian G. |
14th Jun 2010, 10:22 am | #11 |
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Re: RA17W where to start
I'm not familiar with these sets, but the original post describes the capacitors as metallised paper. This could mean capacitors with a paper dielectric housed in a metal can. I've restored some military gear containing such capacitors and they were in excellent condition with hardly any electrical leakage.
On the other hand if metallised paper means waxies replace them all.
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14th Jun 2010, 11:27 am | #12 |
Dekatron
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Re: RA17W where to start
I have an RA17L part way through restoration, and so far have only had to replace faulty resistors (and not too many of those either)
The caps that are fitted to these are indeed Metallised Paper - and are utterly reliable in my experience - the only "waxies" I have found on mine were acting as mains input filter caps - they only lasted a few moments once power had been applied! Seems that RA17s are addictive - I've just purchased two more! Cheers Sean
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5th Jul 2010, 12:06 am | #13 |
Triode
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Re: RA17W where to start
I have repaired many RA17's. Two faults have been the tiny tubular 0.005 caps. One stopped the 1 meg oscillator going. The other was in the 1.6 meg if in a 117, open. Caused 10 db low gain. A pig to find.
If you really must do something, check the ones on the agc line. 10 megohm is ok as there is 470k to ground and 20 meg pulling up to HT! Last edited by Darren-UK; 5th Jul 2010 at 10:04 am. Reason: FPK. |
21st Jul 2010, 2:44 pm | #14 |
Pentode
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Location: Roxburghshire, UK.
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Re: RA17W where to start
If the set has been stored in a shed or garage, shove it in the airing cupboard for a couple of weeks.
First job is to make sure the right valves are in the right holes - never overestimate the previous owners!!! Pull them and replace to give the contacts a wipe, ditto with the crystal. Look for puddles of wax on the bottom covers. I would change those that have left a puddle or are badly blackened and check the resistors in their associated circuits. Check the mains voltage taps. Run it up slowly either with a variac or series 100W bulb and once you have worked up the confidence to apply the mains directly and haven't seen any smoke, do a voltage check on the valve bases you can reach as per the manual. It will probably be running by now anyway. Give all the valves a wiggle to check for noisy contacts You'd be surprised how far off spec components can be, while still allowing the set to work comparatively well. The only duff caps I have ever seen (in the couple of dozen I have had my hands in) actually stopping the radio from functioning completely are the silver micas in the IF strip (C210, 211, 212) and occasionally those in the filter sections. You must have done all this by now anyway, unless you are remarkably patient - does she go? nudge nudge etc... |
22nd Jul 2010, 5:02 pm | #15 |
Heptode
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Re: RA17W where to start
You really must have a very accurate signal generator capable of 40mc/s at least, plus a good scope and the manual is excellent, so if you want one I can PDF it to you, measure voltages, inject signals and measure as directed in the manuals, a lot of times stages can be isolated to narrow down faults
The poisonus capacitors are any of the black Hunts paper ones, the cases are often cracked & open to air and they were all leaky 30 years ago! Other types I have found can be risked if you dont want a huge amount of work |