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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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22nd Mar 2017, 4:33 pm | #1 |
Octode
Join Date: Feb 2010
Location: Leicester, UK.
Posts: 1,431
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HMV 1604 Autogram
Hi all, I am currently repairing one of these table top radiograms. I am having a problem getting power to the set, the deck will rotate and work as it should but the radio chassis is pretty much dead. When I turn it on I can hear a noise coming from the chassis (the kind of warming up tingle from valve envelopes that is normally heard) but there is no valves lighting up, the dial lamps are dead as is the rest of the set. I have tested the dropper on the set and this is showing continuity, the dial lamps also get their power from here so I can't see why they don't light up at all. Anyone know where to start looking?
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22nd Mar 2017, 4:44 pm | #2 |
Moderator
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Location: Exeter, Devon and Poole, Dorset UK.
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Re: HMV 1604 Autogram
This is ISTR and AC/DC set.
You sometimes get a metalic buzzing like this if the Filament circuit is OC. It seems to come from the rectifier when it has AC on the Cathode but isn't hot. So I would start by checking the fialment circuit. Maybe something has gone High resitance or breaks as soon as any current tries to flow. Cheers Mike T
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Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk |
23rd Mar 2017, 2:59 pm | #3 |
Octode
Join Date: Feb 2010
Location: Leicester, UK.
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Re: HMV 1604 Autogram
Cheers Mike,
Looks like one of the KT71s has an O/C heater hopefully changing this will give the set some life. I have noticed the turntable runs slow on this one, it has the original Auto deck in that has capacitors in a box like other EMI motors. I just wondered if anyone could give me the value of these caps? I have the radiomuseum copy of the circuit but I can't make out the values due to the low quality copy, they look to me like 0.15uF but I can't be too sure. Cheers Bren |
23rd Mar 2017, 6:24 pm | #4 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,528
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Re: HMV 1604 Autogram
The manufacturer's data simply says 1.15 no units given.
The Electric Gramophone Motors reference suggests 2uF and talks about "Mansfield" type, whatever that was. I had one of these that I disposed of in the bring and buy at Harpy or RWB a while back. This wouldn't be that one by any chance? I never looked at it, I'd just taken pity on it at an earlier auction and been intrigued by its live chassis P-P amplifier.
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23rd Mar 2017, 7:12 pm | #5 |
Dekatron
Join Date: Sep 2015
Location: Southwold, Suffolk, UK.
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Re: HMV 1604 Autogram
A "Mansfield" condenser is a large paper type in a can, usually of large uF capacity. It will have 2 screw type connectors on the top.
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Edward. |
24th Mar 2017, 1:17 pm | #6 |
Octode
Join Date: Feb 2010
Location: Leicester, UK.
Posts: 1,431
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Re: HMV 1604 Autogram
Thanks for the help so far, I have removed the wax to access the capacitors, sadly no markings. The terminals were on one side of the capacitor much like a radial capacitor so with what Edward said too that is probably what they were referring to by Mansfield. I shall try 2uF and see how it responds, they were quite chunky capacitors, about the same size as other 2uF waxies I have came across before so I would think that the value is correct.
Cheers Bren |
24th Mar 2017, 2:09 pm | #7 |
Octode
Join Date: Feb 2010
Location: Leicester, UK.
Posts: 1,431
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Re: HMV 1604 Autogram
I ordered a 50L6GT to replace the KT71 that had the O/C heater which has arrived. Upon turning the set on I now have a loud hum from the speaker once the valves warm up, hopefully replacement of the remaining capacitors will return it to working order.
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24th Mar 2017, 2:46 pm | #8 |
Octode
Join Date: Feb 2010
Location: Leicester, UK.
Posts: 1,431
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Re: HMV 1604 Autogram
I wonder if anyone can help identify the two capacitors circled below as I am quite sure they aren't on my copy of the service info. I can see the one on the left is marked .002 MFD but that is all I can see as the print has worn away. The other on the right is completely unreadable so I am unsure of the value of this one or the voltage rating of either.
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24th Mar 2017, 2:58 pm | #9 |
Dekatron
Join Date: Sep 2015
Location: Southwold, Suffolk, UK.
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Re: HMV 1604 Autogram
The correct word is Mansbridge, sorry I forgot to add this in earlier. I think you may find your replacement output valve will have a higher slope than the KT71.
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Edward. |
24th Mar 2017, 4:55 pm | #10 | |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
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Re: HMV 1604 Autogram
Quote:
I'm wondering if those tubular ones are the originals as fitted? Lawrence. |
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24th Mar 2017, 5:58 pm | #11 |
Octode
Join Date: Feb 2010
Location: Leicester, UK.
Posts: 1,431
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Re: HMV 1604 Autogram
Hi Lawrence,
Thanks for the help, that is rather strange. It threw me off a bit as my circuit info also has them as Silvered mica caps so I was expecting wax covered micas. The one to the left definitely reads 0.002uF so that is definitely incorrect. I know the set has had work in the past, an RS can is in place of the original 32+32uF can and there is also an extra 32uF electro cap tucked away in the corner of the chassis near that can (this also doesn't appear on the circuit info). I'm hoping that someone hasn't gone in and bodged it all up, it looks like a fairly untouched receiver otherwise. |
24th Mar 2017, 6:23 pm | #12 |
Octode
Join Date: Feb 2010
Location: Leicester, UK.
Posts: 1,431
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Re: HMV 1604 Autogram
Just downloaded the 1115 info sheet and it states there are some differences with the gram chassis, this includes C22 becoming 0.002uF instead of 0.01 due to the set having a tone control. I am going to replace them with silvered micas as the circuit info has them as, but I can't find the working voltage so I will just replace them with 500v ones I have to spare.
Cheers |
24th Mar 2017, 6:30 pm | #13 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: HMV 1604 Autogram
Cheers, yes I missed that, I should have read the whole sheet>
Lawrence. |
28th Mar 2017, 5:10 pm | #14 |
Octode
Join Date: Feb 2010
Location: Leicester, UK.
Posts: 1,431
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Re: HMV 1604 Autogram
Hi, just changed the caps for a pair of 2uF 450v motor run caps, the speed is still slow on it, would anyone know any ideas to speed it up? Is it likely due to the caps that I used?
Regards Brennen |
28th Mar 2017, 5:34 pm | #15 |
Octode
Join Date: Feb 2010
Location: Leicester, UK.
Posts: 1,431
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Re: HMV 1604 Autogram
Also the windings seem to be getting warm too. I presume people have replaced these before as I have had to on other HMV/EMI motors so could anyone advise me as to what they fitted in their players?
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29th Mar 2017, 7:15 pm | #16 |
Octode
Join Date: Feb 2010
Location: Leicester, UK.
Posts: 1,431
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Re: HMV 1604 Autogram
I've managed to get the motor playing, I made up 2x 1.16uF caps out of smaller X2 types. It played well but I have noticed it will run a bit lumpy and overall is a bit sluggish. If I move the centre spindle a bit that helps, it seems to be very critical on where this is in order to operate correctly. I suppose it needs a full strip and rebuild I did give it a quick spray of wd40 just to loosen up any dried grease and stuck parts and this hasn't helped either.
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