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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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16th Jun 2017, 1:26 am | #1 |
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HMV Radiogram Model 2342 Broken Radio
Hello.
The radio (FM, MW and LW) does not work on my unit. No signs of bulging caps, tin-whiskers transistors etc. Where else should I start looking? Many thanks. Oliver. |
16th Jun 2017, 7:59 am | #2 |
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Re: HMV Radiogram Model 2342 Broken Radio
I assume it works as a record player?
You could try cleaning the wave change switches. If that doesn't work you'll have to take voltage readings.
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16th Jun 2017, 11:14 am | #3 |
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Re: HMV Radiogram Model 2342 Broken Radio
Hi.
Yes, the record player works. I will try some contact cleaner on the wave change switches although as all bands are dead, I expect a component has blown. Any idea where I should take voltage readings from? Many thanks. |
16th Jun 2017, 11:19 am | #4 |
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Re: HMV Radiogram Model 2342 Broken Radio
Readings should be taken with respect to the chassis. the expected results are shown in the service sheet.
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16th Jun 2017, 11:21 am | #5 |
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Re: HMV Radiogram Model 2342 Broken Radio
Tin whisker AF117 ETC I expect as per your previous request on this forum.
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16th Jun 2017, 11:40 am | #6 |
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Re: HMV Radiogram Model 2342 Broken Radio
The service sheet for this model is available http://www.service-data.com/section.php/3824/1/2342.
You dismissed the tin whisker transistor problem in your first post but the early version is fitted with AF11x transistors in the AM front-end and the AM/FM IF amplifier; the later version is fitted with AF12x transistors in those positions and don't suffer from tin whiskers. So double check which transistors are fitted in your set. As the gram works and the radio (both AM and FM?) does not, suspicion falls on the IF amplifier. Measure the collector, emitter and base voltages (with respect to chassis as Graham says) on VT4, VT5 and VT6. |
16th Jun 2017, 9:21 pm | #7 |
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Re: HMV Radiogram Model 2342 Broken Radio
* I have the service manual.
* I have cleaned the switch contacts - no change. * Both AM and FM are not working. * I have AF116 transistors - some of the pins are covered in insulation. |
16th Jun 2017, 9:33 pm | #8 |
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Re: HMV Radiogram Model 2342 Broken Radio
AF116's suffer from the 'tin whisker' problem, as do all AF11x and OC17x series transistors
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16th Jun 2017, 9:50 pm | #9 |
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Re: HMV Radiogram Model 2342 Broken Radio
Time for new transistors then?
I am getting voltage on one or two pins at best per transistor... |
16th Jun 2017, 9:52 pm | #10 |
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Re: HMV Radiogram Model 2342 Broken Radio
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16th Jun 2017, 9:56 pm | #11 |
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Re: HMV Radiogram Model 2342 Broken Radio
Ah ha. Thanks.
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16th Jun 2017, 10:05 pm | #12 |
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Re: HMV Radiogram Model 2342 Broken Radio
I would still suggest that you take some voltage readings and check the results before you start changing transistors. At least they'd show which transistors were at fault.
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16th Jun 2017, 10:07 pm | #13 |
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Re: HMV Radiogram Model 2342 Broken Radio
Should I be getting some voltage on all transistor pins?
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16th Jun 2017, 10:18 pm | #14 |
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Re: HMV Radiogram Model 2342 Broken Radio
As Station X said in post 4 the expected voltages are shown on the service sheet.
The Base and Emitter voltages in the main will tend to be quite low. See example in the snip. Cheers Mike T
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16th Jun 2017, 10:19 pm | #15 |
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Re: HMV Radiogram Model 2342 Broken Radio
The voltages you should expect are shown in your manual.
An example is shown below with pinout details. EDIT: post crossed with Mike, interestingly showing exactly the same example. Last edited by ukcol; 16th Jun 2017 at 10:20 pm. Reason: crossed posts |
16th Jun 2017, 10:27 pm | #16 |
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Re: HMV Radiogram Model 2342 Broken Radio
I would add that switch S1A disconnects power from the radio section of the circuit when GRAM mode is selected, so checking for voltage there could be a good starting point.
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16th Jun 2017, 10:32 pm | #17 | |
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Re: HMV Radiogram Model 2342 Broken Radio
Quote:
Actually I chose that one as it was a less cluttered than VT6 and VT4 half is on another page so I guess yours was the same sort of thinking Cheers Mike T
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17th Jun 2017, 8:01 am | #18 |
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Re: HMV Radiogram Model 2342 Broken Radio
As a starting point, give all the AF1xx transistors a good tap, sometimes it gets them working for a while. You then know what the problem is.
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17th Jun 2017, 9:16 am | #19 |
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Re: HMV Radiogram Model 2342 Broken Radio
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17th Jun 2017, 11:08 am | #20 |
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Re: HMV Radiogram Model 2342 Broken Radio
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