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Old 21st Jul 2018, 8:46 am   #1
michalism
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Default Help fixing H.M.V. Model 2116

Hello

I have bought a faulty HMV Model 2116 in order to try fixing and restoring it.
The case is not in a good shape, but that's not my real issue right now.

The initial visual inspection revealed a very dirty, smelly and sticky circuit board, and a few loose cables. However, when I tried to power it up, it seemed to work partially. It was receiving FM (VHF) only, and no other band. The Volume dial was somewhat responsive.

I decided to do a full recap of the unit, before start troubleshooting it. I have also bought the service manual online.

Unfortunately, after I finished with the recapping, the radio seems to be in a worst condition than before!!
When I power it up now, I only get a rattling noise on the speaker, like a helicopter engine or aircompressor. it does that on all bands and the volume is the same no matter what I do with the volume dial.
I have not been able to get a waveform on the scope, and with my meter I measure the frequency at around 24Hz - not sure if this is a reliable measure or if it is of any use!

I can send pictures of the unit if you want.

what I am looking for is some guidance what to start looking for.
The only thing I did was to change the electrolytics and clean the pcb with IPA.
I checked and the wires that are lose are either from the LW/ AM antennas or for the external antenna socket.

I can also attach the service manual if needed.

Any advice would be great!
Thank you very much in advance!
Michalis
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Old 21st Jul 2018, 9:00 am   #2
Boater Sam
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Default Re: Help fixing H.M.V. Model 2116

Quote:
Originally Posted by michalism View Post

I decided to do a full recap of the unit, before start troubleshooting it. I have also bought the service manual online.
That was the first and biggest mistake. Always find out what is faulty first job.

Sounds like it is "motorboating" in the audio section after the volume control.
Check back from the output transformer to the volume control for misconnections.

You changed the reservoir and smoothing caps? Check your work, if its a can, is it earthed ? or has the new can got a plastic wrap ?
Sam.
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Old 21st Jul 2018, 9:09 am   #3
jonnybear
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Default Re: Help fixing H.M.V. Model 2116

I would think you have connected one or two of the capacitors to the wrong points, a few pictures would not go amiss, but do not download the circuit diagram as it is not allowed on this site, and not necessary as most of the people who will reply to your queries will have access to circuits.
John
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Old 21st Jul 2018, 9:26 am   #4
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Default Re: Help fixing H.M.V. Model 2116

Don't rule out mechanical causes either like dirty valveholders, dry joints, dirty switches and cracked print.

vibration from the speaker can set off just such a reaction which sets up a sort of mechanical feedback loop

Cheers

Mike T
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Old 21st Jul 2018, 9:44 am   #5
mark2collection
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Default Re: Help fixing H.M.V. Model 2116

I once had symptoms as described by Mike, in a Westminster radiogram.

Duff HT/smoother & a poor valve socket, the noise was impressive! Mind you, your set has a good number of AFxxx transistors.

Bit late now perhaps, but I take detailed photos before diving in, someone on here may have photos of their set they could upload, sadly, I'm in no position to, not having one of those radios.

Best of luck,

Mark

Last edited by mark2collection; 21st Jul 2018 at 9:50 am. Reason: Detail
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Old 21st Jul 2018, 9:56 am   #6
michalism
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Default Re: Help fixing H.M.V. Model 2116

Hello. Really thankful for taking the time to respond!

Quote:
That was the first and biggest mistake. Always find out what is faulty first job.
I am a little confused on the recapping issue. From what I have read, there are two views: One says do the recapping since this is a really old unit; the other says only change the leaky caps. I decided to follow the first option. Regarding fault finding, since FM seemed to play ok, I figured that most circuits should be working (ie, IF stages and audio amp).
in any case, point taken, and I will be more careful with the next unit!

Quote:
You changed the reservoir and smoothing caps? Check your work, if its a can, is it earthed ? or has the new can got a plastic wrap ?
I will check that. All the caps I used are the ones with the plastic wrap, but I will check again.


Quote:
I would think you have connected one or two of the capacitors to the wrong points, a few pictures would not go amiss, but do not download the circuit diagram as it is not allowed on this site, and not necessary as most of the people who will reply to your queries will have access to circuits.
Thanks for the hint on the schematic, this is why I did not upload it without asking first! What kind of picture do you think would help? the circuit board is quite messy so I am not sure what part to post.

Quote:
Don't rule out mechanical causes either like dirty valveholders, dry joints, dirty switches and cracked print.
vibration from the speaker can set off just such a reaction which sets up a sort of mechanical feedback loop
I am thinking to remove the original speaker and try another one just in case. I have already checked for bad solder joints and that kind of stuff, but everything seems fine.

What really puzzles me is that all I did was to swap the caps, and it stopped working.
I am almost sure I have done some kind of rookie mistake, but can't yet figure it out!

Thanks again for the support!!!
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Old 21st Jul 2018, 10:00 am   #7
michalism
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Default Re: Help fixing H.M.V. Model 2116

Quote:
Originally Posted by mark2collection View Post
Duff HT/smoother & a poor valve socket, the noise was impressive! Mind you, your set has a good number of AFxxx transistors.
I am aware of the problems with the AFxxx transistors, the person you sold me the service manual warned me about this. I have received some AF125's from Germany but I would like to understand what the problem is now before replacing the transistors. Unless somehow it turns out that they are the problem! :p
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Old 21st Jul 2018, 10:52 am   #8
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Default Re: Help fixing H.M.V. Model 2116

I think in your last sentence you are exactly right i.e the AF114/116 were the original fault. You've now introduced a further fault by putting in a capacitor back to front or made a solder bridge across parts or not soldered something correctly so you have a dry joint, all things easily done (I have).

So you need to get it back to the position it was when you first got it. Don't change anything else just get the circuit diagram (you have the ERT one I expect) and check off all the postive/negative connections on the capacitors you have replaced one by one.

Andrew
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Old 21st Jul 2018, 11:02 am   #9
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Default Re: Help fixing H.M.V. Model 2116

Check that the decoupling capacitors across the supply are of the correct value and are connected in circuit correctly, there's one on the battery side of the 180 ohm resistor in the +ve supply feed (100uF) and there's one on the other side of that resistor (350uF)

Lawrence.
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Old 21st Jul 2018, 2:11 pm   #10
michalism
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Default Re: Help fixing H.M.V. Model 2116

This was the first thing I checked also. Both caps are correctly installed. I do have one question though. I do not have a 350uF capacitor, so I used one at 330uF. can this difference have such a dramatic affect? I put a 22uF cap in parallel and made no difference.

I have checked all capacitors by now, and they all seem to have been installed correctly.
I am starting to believe that I have cut a wire by accident or something like that...
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Old 21st Jul 2018, 2:13 pm   #11
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Default Re: Help fixing H.M.V. Model 2116

330uF for 350uF is no problem.

Lawrence.
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Old 21st Jul 2018, 2:27 pm   #12
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Default Re: Help fixing H.M.V. Model 2116

Recapping is advocated by many people, but only for pre 1960s sets fitted with waxed paper capacitors. Capacitor faults can exist in later designs but they are not common enough to justify automatic recapping. The caps in your radio were probably OK.

If you are a beginner and changing a lot of caps, you should do them one by one testing each time. This is to ensure that you haven't introduced a fault.

Check carefully for bits of solder or wire strands bridging circuit tracks, and bad solder joints causing a bad connection.
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Old 21st Jul 2018, 4:20 pm   #13
michalism
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Default Re: Help fixing H.M.V. Model 2116

Thank you for clarifying the recapping question for me.
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