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Old 26th Jun 2020, 12:48 pm   #1
ciaoflyer
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Default HMV Radiogram 2346 Repair

Hi all

Hope you can set me on the right course. I have recently purchased a 1970/1 HMV Radiogram 2346. The reason for this is because my parents had one when I was a child and I have been after the same model since they disposed of theirs in the local landfill

I have finally got one in very good condition cosmetically so well chuffed. The BSR Gram works great and plays records well.

The main problem is the radio as it does not work, lots of crackle but I cannot get any reception on any band, they all sound the same. I believe this is a common problem because of its age so can anyone advise on the route i should take, I am very handy with a soldering iron if parts need replacing.

I have had the back off and it looks like the insides have never been touched, even a little component drawing stapled to the bottom of the cabinet.

Look forward to your help

Cheers
ciaolflyer
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Old 26th Jun 2020, 1:19 pm   #2
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Default Re: HMV Radiogram 2346 Repair

Your set may have the dreaded AF116's tin wisker problem transistors, it seems they used AF11* or AF12* the later not suffering tin whiskers.

It's also got a big bank of switches that will need cleaning.

I think that's where I would start.

Check for the AF11*'s if they are all AF12* then clean the switches.

Cheers

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Old 26th Jun 2020, 1:22 pm   #3
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Default Re: HMV Radiogram 2346 Repair

Great, which transistors can I replace them with?
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Old 26th Jun 2020, 1:23 pm   #4
Edward Huggins
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Default Re: HMV Radiogram 2346 Repair

First of all I would spray the push button waveband selectors with Servisol 10 and actuate them to clean the contacts. Also is the tuning moving freely from side to side?
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Old 26th Jun 2020, 1:41 pm   #5
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Default Re: HMV Radiogram 2346 Repair

Quote:
Originally Posted by Edward Huggins View Post
First of all I would spray the push button waveband selectors with Servisol 10 and actuate them to clean the contacts. Also is the tuning moving freely from side to side?
Thanks, I have sprayed with Servisol and actuated them but this makes no difference at all, may have a second go at it. Tuning work smoothly.
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Old 26th Jun 2020, 1:53 pm   #6
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Default Re: HMV Radiogram 2346 Repair

See this Thread

https://www.vintage-radio.net/forum/...d.php?p=807155

Cheers

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Old 26th Jun 2020, 2:00 pm   #7
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Default Re: HMV Radiogram 2346 Repair

This is all great stuff, thanks for your replies! I have now read on this site that you can dismantle the transistor and remove the whiskers! Gonna have a go and see what happens! Cheers all! Will keep you updated with progress!
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Old 26th Jun 2020, 3:12 pm   #8
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Default Re: HMV Radiogram 2346 Repair

I assume it is the 4 circled in red which are the offending items, is this correct?

They are labeled:

3 x AF116
1 x AF115

I assume I have to remove the board in order to solder them, is this a difficult task? Could I snip them out and then re solder them back?
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Old 26th Jun 2020, 5:11 pm   #9
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Default Re: HMV Radiogram 2346 Repair

They are the offenders, if not faulty now likely will be in the not too distant future. If you cut them out will the leads be long enough to refit?

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Old 26th Jun 2020, 6:47 pm   #10
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Default Re: HMV Radiogram 2346 Repair

It's unlikely you'll need to replace any of those AF*** transistors.

Normal transistors have three leads, the AF*** types have four leads. This extra lead is a silly screen lead which causes problems due to the dreaded tin whisker problem. Download the data sheet for the transistors and identify the "screen" lead and just snip it off on each one and your radio will work - make sure you hit the right lead otherwise you'll have problems. If you want to be less of a butcher then you can carefully un-solder the lead from the board on each one and bend it up out of the way, but it doesn't really matter which method you use. I've never had a recurring problem doing this, so worth a try before going to all the trouble of actually finding replacements and changing them.
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Old 26th Jun 2020, 9:26 pm   #11
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Default Re: HMV Radiogram 2346 Repair

I read somewhere on here that putting a hot soldering iron on the case for a few seconds melts the whiskers and the transistor starts working. Worth a try before you start undoing things
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Old 27th Jun 2020, 6:14 pm   #12
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Default Re: HMV Radiogram 2346 Repair

Update: It is deff the transistors so thanks to all! I have tried heating with soldering iron but it did nothing. So then I tapped them and one of them made a loud cracking sound, nothing from the others. After tapping a bit more LW sprang into life on Radio 4! However, after switching off it did not work again, so may need to dismantle!

I did fine a parts guarantee inside, do you think they will still honor it?
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Old 27th Jun 2020, 7:16 pm   #13
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Default Re: HMV Radiogram 2346 Repair

Another strange note that when the radio is working, if I tap the tuning knob, it gets louder.
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Old 27th Jun 2020, 7:31 pm   #14
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Default Re: HMV Radiogram 2346 Repair

Tommy Cooper would probably have said "well don't tap it then"
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Old 28th Jun 2020, 8:35 am   #15
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Default Re: HMV Radiogram 2346 Repair

I usually replace all four with AC125’s. Double check the pin outs but they will be a straight fit onto the board.
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Old 28th Jun 2020, 11:16 am   #16
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Default Re: HMV Radiogram 2346 Repair

Do you mean AF125s Michael?

AF11x transistors are usually straightforward to replace and lots of substitute types will work. Even silicon types will often work despite the different bias requirement. There are many threads on AF11x replacement if you search the forum.
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Old 29th Jun 2020, 11:29 pm   #17
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Default Re: HMV Radiogram 2346 Repair

Sorry Paul yes AF125's
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Old 1st Jul 2020, 3:09 pm   #18
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Default Re: HMV Radiogram 2346 Repair

would these be ok to replace with:

https://www.cricklewoodelectronics.c...QaAkWgEALw_wcB

Please remove if this post is not allowed - Thanks
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Old 1st Jul 2020, 3:17 pm   #19
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Default Re: HMV Radiogram 2346 Repair

No, you cant fit a silicon transistor in place of a germanium without modifying the bias conditions. In any case a BC transistor is for low frequencies like audio.

You can use these
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Old 1st Jul 2020, 3:22 pm   #20
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Default Re: HMV Radiogram 2346 Repair

Just do as I said and isolate the screens on all the AFs and the job's done. You can look into possible replacements should you have problems further down the line and need to actually replace them. I find that clipping or lifting the screen to each transistor cures the fault, although in theory a 'whisker' could actually short across the junction rather than just junction to screen, but this is very rare.
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