27th Feb 2020, 2:52 pm | #201 |
Dekatron
Join Date: Jul 2008
Location: Kington, Herefordshire, UK.
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Re: Grundig TK 819 Any Useful Info
These connectors are as rare as rocking horse dropppings, having been dropped in favour of DINs after this series. One may turn up on auction sites, but then it needs the vendor to realise what it is, so reaming may be the better choice...
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27th Feb 2020, 5:22 pm | #202 | |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
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Re: Grundig TK 819 Any Useful Info
Quote:
For screen grid basics see second paragraph of book page 9 here: https://www.kevinchant.com/uploads/7...ube_manual.pdf Lawrence. |
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27th Feb 2020, 6:07 pm | #203 | |
Octode
Join Date: Mar 2006
Location: Lund, Sweden
Posts: 1,632
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Re: Grundig TK 819 Any Useful Info
Quote:
I once makeshifted a plug by wrapping an long M3 or M4 screw with scotch tape so that the resulting contraption was 6mm in diameter. That at least made contact with the inner part of the socket. An idea would be to take something like a round standoff with a 6mm outer diameter (such as this one: https://uk.rs-online.com/web/p/round-spacers/1022326/), put some sort of insulation in the bore, such as heat shrink tubing, and screw an M3 screw into the tube. It won't be pretty but could be reasonably functional and wouldn't necessitate carving up the '819. Or indeed something like this https://uk.rs-online.com/web/p/round-spacers/1418506/ where the flange would stop it getting pushed in to far. |
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27th Feb 2020, 6:51 pm | #204 |
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Re: Grundig TK 819 Any Useful Info
Yes a reamer would be more gentle/controlled than a drill, I have a couple somewhere but not sure if they will be large enough.
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27th Feb 2020, 6:53 pm | #205 |
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Re: Grundig TK 819 Any Useful Info
Great book Lawrence thank you.
David |
27th Feb 2020, 6:56 pm | #206 |
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Re: Grundig TK 819 Any Useful Info
I occasionally see old jack plugs/jack plug cables at car boot sales, will have to keep my eyes open and take my calipers to measure any found.
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27th Feb 2020, 9:28 pm | #207 |
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Re: Grundig TK 819 Any Useful Info
Borrowed a 1.2 Mohm resistor (R2) from my TK 5 and fitted it into the TK 819 as a temporary replacement for the open circuited R9 (1.25 Mohms).
Now get more normal voltages at the EF 86 valve, namely 33 volts at pin 5 Screen Grid (G2) and 45 volts at pin 6 (Anode) and the HT voltage at top end of R9 has dropped down from previous 200 volts to 166 volts. The HT voltage the other side of R10 which feeds R9 and R8 (anode resistor) is 199 volts. Note - TK 819 schematic shows 100 volts at top end of R8, for various reasons I think this is incorrect/not accurate. So the Screen Grid resistor made a substantial difference to the anode voltage (thankfully). No obvious visual change to the EF 86 brightness. |
28th Feb 2020, 11:43 am | #208 |
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Re: Grundig TK 819 Any Useful Info
The removed microphone transformer.
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1st Mar 2020, 6:19 pm | #209 |
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Re: Grundig TK 819 Any Useful Info
Attached are photos showing 4 standard size (1/4") jack plugs that will not fit plus the slightly smaller one that does fit.
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1st Mar 2020, 7:08 pm | #210 |
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Re: Grundig TK 819 Any Useful Info
You could get some brass jack plugs skimmed, perhaps?
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1st Mar 2020, 9:10 pm | #211 |
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Re: Grundig TK 819 Any Useful Info
From a separate post someone has offered to sell me some brass ones after he turns them down to 6mm.
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11th Mar 2020, 4:57 pm | #212 |
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Re: Grundig TK 819 Any Useful Info
After replacing the open circuit R9 (at Post # 207) on the EF 86 valve and restoring normal anode & grid voltages, tried playing a tape again and was amazed that now get half reasonable playback sound with plenty of volume ! so this is somewhat encouraging
Now need to test recording and also try and get the clutch rubber replacement material work looked at (although may be a waste of time on the Take Up hub as no solenoid wiring). Also need to get back to the GI/GII contact set operation for the 7.5 ips speed changeover by the centrifugal motor action, previously was struggling to get GI contacts to electrically to make. |