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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc. |
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4th Apr 2021, 11:26 am | #41 |
Dekatron
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Re: Reps JC20 Reel to Reel
Here's a link to the full article (starts at mag. page 42):
https://worldradiohistory.com/Archiv...UK-1958-10.pdf Spot the problems with the components list... Lawrence. |
4th Apr 2021, 1:10 pm | #42 |
Triode
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Location: Norwich, Norfolk, UK.
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Re: Reps JC20 Reel to Reel
Thank I save the link. But have to say all my tape players, keyboards, are just on show never use for making music any more old and out of date all done on computers so what do I save and put money ? this one is the same age as me and was going to a coffee table with a glass top. Les
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4th Apr 2021, 1:24 pm | #43 | |
Dekatron
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Re: Reps JC20 Reel to Reel
Quote:
K instead of k for kOhms. ohms instead of Ohms. mfd instead of mFd (now commonly uF/Micro Farad), the m in mfd indicating micro not milli here of course. pf instead of pF or pFd (for pico Farad). No heater pins/voltages reference. But I think you may have spotted something more fundamental ? David |
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4th Apr 2021, 1:30 pm | #44 |
Dekatron
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Re: Reps JC20 Reel to Reel
Plus no power ratings for the resistors and no voltage ratings for the capacitors.
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4th Apr 2021, 1:32 pm | #45 | |
Dekatron
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Re: Reps JC20 Reel to Reel
Quote:
C31 isn't listed. Lawrence. |
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4th Apr 2021, 1:37 pm | #46 | |
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Re: Reps JC20 Reel to Reel
Quote:
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4th Apr 2021, 1:47 pm | #47 |
Dekatron
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Re: Reps JC20 Reel to Reel
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4th Apr 2021, 2:36 pm | #48 |
Triode
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Location: Norwich, Norfolk, UK.
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Re: Reps JC20 Reel to Reel
As I don't understand resistors and capacitors the only mistake I see was in taking it apart
If you remove the speaker from the front board it will go through the hole and the 2 wires the other end are in a block connector and all 3 parts come out as one |
4th Apr 2021, 2:48 pm | #49 | |
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Re: Reps JC20 Reel to Reel
Quote:
David |
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4th Apr 2021, 2:56 pm | #50 | ||
Octode
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Re: Reps JC20 Reel to Reel
Quote:
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4th Apr 2021, 4:49 pm | #51 |
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Re: Reps JC20 Reel to Reel
Just another observation, the representation of the level indicator valve in the schematic and its connection to the circuit looks wrong to me.
Lawrence. |
5th Apr 2021, 10:55 am | #52 |
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Re: Reps JC20 Reel to Reel
I am not really au fait with Magic Eye representations/circuit connections, especially the EM 71.
Looking at the schematic now there are several things that look somewhat different to typical:- 1. The anode for the triode amp section of the valve normally has a load resistor, with the display section anode normally being connected directly to +HT, in the schematic the load resistor R34 is shown on the anode for the display section (although sometimes both anodes share a load resistor). 2. The record signal to be monitored is connected through to the control grid of the triode amp section (via various components) from the output of the EL84 output Pentode, typically the record signal is tapped off at the preceding amplifier valve. 3. The way the two grids are drawn, looks a little different from typical. Sometimes they are drawn as if they are a single grid (whereas in fact they are 2 separate grids) with the record signal connected to the left hand side of the grid and the right hand side of the grid connected to the grounded cathode. Other times the 2 grids are drawn as 2 grids with height displacement (i.e. not in line). The way the display grid on the right hand side is shown connected down to the cathode could infer that it is an internal connection, whereas the display grid connects out to pin 6, so I think there has to be an external wire connecting pin 6 back to the cathode (pin 7). 4. The Deflection electrode (if that is the correct name) is not drawn, this is sometimes shown connected internally to the triode anode. With your Eagle eyes Lawrence you may well have spotted something more fundamental. David |
5th Apr 2021, 11:03 am | #53 |
Dekatron
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Re: Reps JC20 Reel to Reel
The lack of an anode lode for the amplifier section was the giveaway for me.
Lawrence. |
5th Apr 2021, 3:03 pm | #54 |
Triode
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Re: Reps JC20 Reel to Reel
Have just done some cleaning and maintenance mechanical side only I did notice any main moving parts seem to have a separate washer inside In taking these out they had felt oil retainer rings So mechanically it was very well thought out Prosper bronze bushing so it was well worth saving for future generations les
Last edited by Starlight 1; 5th Apr 2021 at 3:06 pm. Reason: text |
6th Apr 2021, 2:02 pm | #55 |
Triode
Join Date: Apr 2021
Location: Norwich, Norfolk, UK.
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Re: Reps JC20 Reel to Reel
I move it from floor standing over night its in a bad way old oil on the floor taking it all back out and it was coming from ,( Hunts cap DC red (res)32uf 450v max ripple 275 ma yellow 32uf 450v one line I can not see kb564 hub so its looking like a full set in this one as it was only on for 2 or 3 mins on Sunday for a test ps this is on the main power board.
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6th Apr 2021, 8:40 pm | #56 |
Dekatron
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Re: Reps JC20 Reel to Reel
Does the can capacitor your describe look original ? the parts list does not show any 32uF.
What is the kb564 hub ? David |
6th Apr 2021, 9:06 pm | #57 |
Triode
Join Date: Apr 2021
Location: Norwich, Norfolk, UK.
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Re: Reps JC20 Reel to Reel
Yes it looks original it's aluminium with an aluminium casing to hold it in.
I have put down what it says on the side and the one next to it end up in KB562 hub is the last lettering on this one which is slightly smaller |
10th Apr 2021, 4:36 pm | #58 |
Triode
Join Date: Apr 2021
Location: Norwich, Norfolk, UK.
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Re: Reps JC20 Reel to Reel
I see I put HUB after moving it from the cover its HUD
Last edited by Starlight 1; 10th Apr 2021 at 4:36 pm. Reason: text |
10th Apr 2021, 5:37 pm | #59 |
Dekatron
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Re: Reps JC20 Reel to Reel
Assume that KB 564 is a manufacturers number for that particular dual can capacitor, HUD may be an abbreviation for a vendor?
David |
10th Apr 2021, 5:53 pm | #60 |
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Re: Reps JC20 Reel to Reel
It hardly matters. If it's faulty just replace it with a generic component having the correct values.
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