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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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28th Jun 2020, 12:21 pm | #21 |
Dekatron
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Re: Ferrograph Re-capping
I would replace it too, its resistance affects the voltage supply for V2,V3,V4 & V7 heaters and the supply to the solenoid circuit.
Lawrence. |
28th Jun 2020, 12:26 pm | #22 |
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Re: Ferrograph Re-capping
I agree, the resistance is a long way out, but have you checked what the meter reads with just the meter leads connected together? what ever that resistance is, it will be added to the actual resistor resistance.
I am not really sure of the function of R6, not sure about the smoothing reference. |
28th Jun 2020, 12:36 pm | #23 |
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Re: Ferrograph Re-capping
Surge limiter.
Lawrence. |
28th Jun 2020, 12:38 pm | #24 |
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Re: Ferrograph Re-capping
Have you measured the DC supply at C10 to see how close it is to the 11V shown on the schematic ?
Do you know what this solenoid function is, is it to do with EOT (End Of Tape) detection and stopping the drive ? David |
28th Jun 2020, 1:13 pm | #25 |
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Re: Ferrograph Re-capping
The solenoid holds the start control in position when the control is set to start, apart from switching off the mains it's de-energized by the stop button switch or the auto stop switch, these switches short out the solenoid, hence the 100 Ohm series resistor.
Lawrence. |
28th Jun 2020, 3:27 pm | #26 | |
Pentode
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Re: Ferrograph Re-capping
Quote:
I will order and swap out a few resistors since R76 also appears closer to 2K2 than 1K8. Worth putting carbon comps back in here or would it make more sense to go metal film or wirewound? Also, in place of R1 (100R) there appears to be a pair of 100R resistors in parallel. Possible repair? Thankyou for everyone's contributions so far |
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28th Jun 2020, 5:09 pm | #27 | |
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Re: Ferrograph Re-capping
Quote:
With electrolytics, the tolerance is so great + or - 25 or 30% is quite normal.
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30th Jun 2020, 11:30 am | #28 |
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Re: Ferrograph Re-capping
I do find that other digital capacitance reading meters (non DVM type) generally give similar readings to the DVM reading.
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1st Jul 2020, 12:08 pm | #29 |
Pentode
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Re: Ferrograph Re-capping
Thanks for the advice regarding the readings, I'll take that into account. At the moment I'm just waiting on delivery of a couple of bits then I can put the PSU back together. I couldn't source any 25mm diameter 16+16 cans so I went with a 35mm and a new clip - it will not be centered but there's just enough give that the pins won't touch the chassis. I'm going to insulate them anyway to be on the safe side. There is actually an unusued 35mm hole cut in the chassis, perfectly suited to the bigger can, but it would mean trying to unpick some wires from the bundles to relocate them.
I aim to swap out the 16+16 can and the 8uF on the power supply, along with the 2R2 on the 4700uF filter cap, the 1K8 (which might be fine but I thought I may as well) and the 100R near the solenoid. All using modern carbon films. Once that's done I'll re-evaluate and then look at the amp section! |
1st Jul 2020, 11:20 pm | #30 |
Pentode
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Re: Ferrograph Re-capping
Quick question - schematic says there should only be a 100 ohm resistor here. Is the chunky one also a resistor?
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1st Jul 2020, 11:28 pm | #31 |
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Re: Ferrograph Re-capping
Yes definitely a 100 ohm resistor, larger power (wattage) rated than the smaller one.
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1st Jul 2020, 11:30 pm | #32 |
Pentode
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Re: Ferrograph Re-capping
Thanks David, I thought so, just wasn't sure if it might be some kind of axial cap or something. Unsure why it's in there, should only be a 1W resistor. Going to pull them both out and swap them for a single 1W 100R, as per the diagram
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1st Jul 2020, 11:36 pm | #33 |
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Re: Ferrograph Re-capping
If they are in parallel first try measuring their combined resistance, should be around 50 ohms if both are intact.
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2nd Jul 2020, 1:17 am | #34 | |
Pentode
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Re: Ferrograph Re-capping
Quote:
Put everything back together and fired it up. The solenoid seems to be holding now, but even though it does, it doesn't always seem to keep the capstan motor running. Sometimes it does, other times you have to keep the lever held hard (even though the solenoid is holding it) to shift it what feels like a millimeter, then you hear the motor start whirring again. This seems to go for play, FF and RW in all speeds. Not sure if perhaps some mechanical adjustment is therefore necessary? Or maybe just dirty contacts? Despite all this, the reel tables (correct term?) don't revolve; It has just wound a lot of tape around the capstan because the take up reel didn't move. I'm guessing that points to duff motors which is probably a bit beyond my remit unfortunately |
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2nd Jul 2020, 1:05 pm | #35 |
Octode
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Re: Ferrograph Re-capping
I would leave the high voltage 16+16uf cap in place, unless it's leaking electrolyte, getting hot during use, etc. They often measure up to +50%, so ~22uf measurements are normal.
Same goes for the 8uF cap, ~9uf measurement is absolutely fine. ** Remember to always wait for these caps to fully discharge before taking measurements!! **
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2nd Jul 2020, 1:42 pm | #36 | |
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Re: Ferrograph Re-capping
Quote:
If it was me, I would replace with either a single 47 ohm 1 watt or two 100 ohms in parallel. It's just the sort of thing that might cause the solenoid latching problem you are experiencing (depending where the resistor is in the circuit of course).
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3rd Jul 2020, 9:59 am | #37 | ||
Pentode
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Re: Ferrograph Re-capping
Quote:
Quote:
Also it seems like the motors are the issue. Capstan seems to be fine, but the wind back and wind on don't move. In FF and RW, the hubs each spin freely by hand so I'm guessing it's not a lubrication or bearing problem? Can anyone offer advice on where to look here? |
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3rd Jul 2020, 10:58 am | #38 |
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Re: Ferrograph Re-capping
According to the schematic that's been posted the supply and take up motors in FF or Rew are supplied from the same point as the capstan motor which is the 245 volts supply on the mains transformer via switches S1a,b & c, S3 and plug and socket P3 & SK3, the relevant pin/socket numbers for the FF and Rew supply on P3-SK3 are 2 & 7.
On playback or record the supply motor is out of circuit and the take up motor is connected to the 150 volts supply on the mains transformer again via the same switches and plug and socket but this time the relevant pin/socket numbers on P3 & SK3 are 10 & 11. I would check the switches and P3/SK3 contacts If that helps. Lawrence. |
4th Jul 2020, 11:17 am | #39 |
Pentode
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Re: Ferrograph Re-capping
Morning all,
A development! I've spent some time today following continuity from the connectors and through the tagboard, to see where each wire goes to in relation to the wind on/back motors to make sure it wasn't a bad connection (thanks Lawrence!) Through this I've discovered the culprit - one half of the big switch that puts the motors into circuit (with the pair of 0.1uF caps across it) didn't appear to be making any contact when the play lever was engaged. Other half seems fine, so I wondered if perhaps it had just come loose or deformed with age and needed some help. Clipped my DMM to the contacts, pulled the lever closed and reached in to give the long, brass strip a little nudge - at which point it twisted at an angle and stayed there. Looks like there is a fracture in the brass strip halfway down, where it bends, and I've just helped it along by moving it. It would make perfect sense that the contact responsible for the winding motors is broken, and since the other isn't - the capstan motor still runs. So! Looks like all I need to do is swap out the strip (although I may as well do both) and I'm good. I may be able to source a replacement switch, and I guess at a push it's not too difficult to make a new strip if I can get the contact point on there and match the angle etc. Going to remove it so I can take a closer look. |
4th Jul 2020, 11:43 am | #40 |
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Re: Ferrograph Re-capping
Well done ! and good luck with sourcing replacement switch/repairing, may not be easy.
David |