27th Apr 2017, 9:20 pm | #1 |
Tetrode
Join Date: Mar 2016
Location: Chulmleigh, Devonshire, UK.
Posts: 88
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Decca TP 44
Hi
I've been restoring a Decca TP44 which I recently bought from ebay.I have repaired the case and handle and it's looking really nice it's the light blue colour which was filthy and discoloured when I received it. I matched the colour with Humbrol enamel and painted it and it turned out really well.It didn't work when I received it which I found was the hacker type of multi pinned plug which connects the amp to the rest of the circuit a good clean got it going.However although the reception on L.W.is loud and clear M.W. is very quiet. I've checked the aerial and all seems OK and I don't think it's an alignment problem any suggestions before I delve any further. Terry |
27th Apr 2017, 9:39 pm | #2 |
Octode
Join Date: Jan 2003
Location: Guildford, Surrey, UK.
Posts: 1,958
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Re: Decca TP 44
Have you cleaned the wavechange switch contacts?
If so, then I'd check the MW RF alignment. Ron |
27th Apr 2017, 9:45 pm | #3 |
Tetrode
Join Date: Mar 2016
Location: Chulmleigh, Devonshire, UK.
Posts: 88
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Re: Decca TP 44
Hi Ron
I've checked them both and I think they are o.k. but I will look again to see if I missed anything Terry. |
27th Apr 2017, 9:59 pm | #4 |
Octode
Join Date: Jan 2003
Location: Guildford, Surrey, UK.
Posts: 1,958
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Re: Decca TP 44
Does C2 peak the high frequency end (around 230m) nicely or is the tuning point rather 'flat'?
Ron |
28th Apr 2017, 8:27 pm | #5 |
Tetrode
Join Date: Mar 2016
Location: Chulmleigh, Devonshire, UK.
Posts: 88
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Re: Decca TP 44
I'm not to sure what you mean about c2 Ron as my knowledge is a bit sketchy.I checked the alignment by ear as I don't have the test gear.I moved the trimmers and cores slightly one by one and the best reception was obtained by them all in their original position.The wave change switch is all clean and works as it should. By the looks of the it the innards all look pristine and unmolested.
|
29th Apr 2017, 11:14 am | #6 |
Rest in Peace
Join Date: May 2003
Location: Harlaxton, Lincolnshire, UK.
Posts: 3,944
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Re: Decca TP 44
Hello Terry,
Since you say that your knowledge is a bit sketchy please allow me to lead you through this problem in more detail. 1] I don't know what to expect from medium wave in Devon, so check by comparison with another radio that your Decca's MW performance is definitely down. 2] Check that the stations you can receive on MW, albeit poorly, are appearing at the correct point on the dial. To do this you will need to find out the wavelength or frequency of your local station(s). If the stations are significantly displaced from their correct positions you will have to go down the alignment route because your local oscillator adjustments will be wrong and will not track correctly with the RF section. 3] With the radio switched OFF and using a digital multi-meter on the Ohms range (if you haven't got a DMM, one good enough for this sort of work can be bought very cheaply from DIY stores) clip the black lead to the metal case of the tuning capacitor and clip the red lead to the RF section tag of the tuning capacitor. I think the RF section is the one nearest the front of this set. With the wave-change switch in the LW position the meter should read about 7 ohms (allow a 20% tolerance). This establishes that the DMM is correctly set and connected. Switch the radio to MW and the reading on the DMM should change to about 2 Ohms. If you get a 2 ohm reading the the MW aerial coil has continuity and the associated wave-change switch contact is also good. If the reading is very high then check the wave-change switch again. If the reading is open circuit then check the MW aerial coil and its wiring. 4] If you haven't found anything wrong yet, check that the MW aerial coil is not loose on the ferrite rod aerial. The MW coil is the one on the left as viewed from the back of the set. If the coil has moved and the alignment of the set hasn't been disturbed you can move it on the rod for best results on a weak station. If the alignment has been disturbed this adjustment will have to be done at the low frequency end of MW as part of the full alignment procedure. |
29th Apr 2017, 8:32 pm | #7 |
Tetrode
Join Date: Mar 2016
Location: Chulmleigh, Devonshire, UK.
Posts: 88
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Re: Decca TP 44
Hi
I've done as you suggested LW reading 8 ohms and MW 4 ohms but strangely enough LW was even Fainter when I switched on today.Both coils are still fixed firmly to the ferrite rod with the original wax.My other radios are picking up LW and MW with no problem.The Decca is picking up the stations in the correct positions on the dial Terry. |
29th Apr 2017, 11:26 pm | #8 |
Octode
Join Date: Nov 2010
Location: Cullompton, Devon, UK.
Posts: 1,434
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Re: Decca TP 44
I would be looking at those dodgy Hunts capacitors and the electrolytic s.
John |
30th Apr 2017, 10:40 am | #9 |
Rest in Peace
Join Date: May 2003
Location: Harlaxton, Lincolnshire, UK.
Posts: 3,944
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Re: Decca TP 44
Hi Terry
Thanks for reporting back to us. That has eliminated some possible causes and it's looking less and less likely that you have an alignment problem. Follow John's advice about the capacitors next. If you haven't got the service data the manufacturer's data is here. |
30th Apr 2017, 3:40 pm | #10 |
Tetrode
Join Date: Mar 2016
Location: Chulmleigh, Devonshire, UK.
Posts: 88
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Re: Decca TP 44
Thanks for all of your advice . There are plenty of Hunts caps and electrolytics in the radio I will start looking at these asap and will report back, it may not be for a while as I have a lot of work commitments
Thanks again Terry |
1st May 2017, 7:15 pm | #11 |
Pentode
Join Date: Sep 2011
Location: Bideford, Devon, UK.
Posts: 196
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Re: Decca TP 44
Hi Terry
If you're still having problems after replacing the hunts caps drop it over and I will check the alignment for you. Don. |