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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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Old 19th Mar 2019, 9:16 pm   #61
Uncle Bulgaria
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Default Re: Ferrograph 4A: Restoration advice needed

Right, so the circuit would be loaded by the same amount if the measurements were taken at the same range, but some just wouldn't cause significant deflection? Changing the range would alter the load and the service document values would reflect this, I suppose?

I'm going to check with the AVO as soon as I get it out, and see if that made the difference.

I'm in the process of adding the modification written up by 'Pichacker' in another thread from a few years ago, when he was fixing up a Vortexion. It's an RC filter on V3's grid, to block DC and give a constant grid-leak rather than the current arrangement where the volume control is the grid-leak. That will be done tomorrow when I get some more yellow capacitors.

I have also put a tape on, and shock horror! it plays. I'm really chuffed, and it's thanks to the input I've had here that I've been able to make sense of a lot of the work I've had to do.

Now the adjustment begins...
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Old 19th Mar 2019, 9:42 pm   #62
ms660
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Default Re: Ferrograph 4A: Restoration advice needed

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Right, so the circuit would be loaded by the same amount if the measurements were taken at the same range, but some just wouldn't cause significant deflection? Changing the range would alter the load and the service document values would reflect this, I suppose?
About the most important circuit to learn and commit to memory in all this learning stuff is the potential divider, that's because all circuits are comprised of them, watch this "old school" training film which shows the effect of loading a potential divider circuit, it's one of the most important lessons you can learn in this game.

https://www.youtube.com/watch?v=wVpL3csYZ5E

Lawrence.
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Old 20th Mar 2019, 12:06 am   #63
Uncle Bulgaria
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Default Re: Ferrograph 4A: Restoration advice needed

That's a great video, Lawrence! I remember in my A-level physics that I never grasped the rheostat/potential divider and their differences. That old USAF man explains it quite well.

Well, let's see - the DMM has a very high input impedance so as a 'load device' there is very little current flow, and its parallel resistance alters the other resistances very little too.

Am I on the right track? That man is so persuasive that it feels as though one understands every word, even if that may not really be the case!
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Old 20th Mar 2019, 12:03 pm   #64
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Default Re: Ferrograph 4A: Restoration advice needed

Yes, that's a good training film, there's more like that on Youtube.

Yes, you're on the right track, but be aware that the input resistance of some DMM's can be lower than the input resistance of a 20k per volt meter that has the 100 volt range selected.

You can probably figure out by now why some voltage measurements are different when measured with meters of different specs.

Also be aware that the voltages given in service manuals etc are not set in stone, in the real world they can vary from those given even when the unit is working as it should.

Keep at it.

Lawrence.
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Old 20th Mar 2019, 1:38 pm   #65
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Default Re: Ferrograph 4A: Restoration advice needed

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I'm in the process of adding the modification written up by 'Pichacker' in another thread from a few years ago, when he was fixing up a Vortexion. It's an RC filter on V3's grid, to block DC and give a constant grid-leak rather than the current arrangement where the volume control is the grid-leak. That will be done tomorrow when I get some more yellow capacitors.
I’ve done this ‘mod’ to a couple of Vortexions too, and can report that it is worthwhile. The volume control is quieter in operation with the DC blocked.

Bill
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Old 20th Mar 2019, 2:49 pm   #66
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Default Re: Ferrograph 4A: Restoration advice needed

I've certainly seen some of the marvellous Pathe-and-similar films that cover everything from the manufacture of Blackpool Rock to how to remember to shoot 3 rads in front of Messerschmitts! In this case, I wouldn't want to be taken for such a greenhorn that I was worried about a few volts here and there, but it was strange to me that the HT could be well within tolerance, yet some of the Va values could be 50% out and still have normal function.

I then thought that the DMM is 'auto-ranging': does this load the circuit differently, as with using an AVO with the "ohms/volt*full scale" because there will be a different full-scale requirement when the digital meter trips to the next higher range? Or doesn't it work like that because the display is not a current-driven pointer?

Thank you Bill - I see you've popped over to Tapeheads as well! I'm really pleased with how this is turning out, so thought plastering some more pictures around the place would help anyone else in a similar situation. I know when I first started pulling this apart I couldn't find any reasonable images of a 4A's innards from anyone on a similar journey so there was a lot of trial and error.

I need to do what you've done and show the changes on the circuit diagram - the trouble is I haven't got it printed large enough to add to yet, so I've just got notes, highlighted components and bundles of paper! I prefer how the Ferrograph manual labels the components with their numbers for the accompanying list, rather than how Vortexion have done it.

Advanced question: The replay head is mounted on four screws over a bar to allow it to tilt sideways. (The space for the dummy head with its spring-loaded octal socket seems the much better design for adjustment). What is the process to get the best response and get the head perpendicular to the tape?

After a forum search I get the principle, and I have TIMTAPE's handylap manual which covers the theory of azimuth/zenith etc. I have no other reel to reel in a usable or calibrated condition to produce a tape but I do have an oscilloscope I could use under instruction if that helps.
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Old 20th Mar 2019, 3:41 pm   #67
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Default Re: Ferrograph 4A: Restoration advice needed

For head azimuth adjustment you need a known good recording that's been done on a machine that's been set up correctly or a correctly recorded test tape that has a high frequency test tone on it.

Failing that, if there is a wear ridge on the head you can align to that to get you in the ball park to how it was before if you have a keen eye and a magnifying mirror.

Lawrence.
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Old 21st Mar 2019, 5:20 pm   #68
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Default Re: Ferrograph 4A: Restoration advice needed

Right. So I'll have to beg, borrow or steal one of those then! Or supply a tape for someone to record a test tone on.

The head that's on there has 'keystone' wear which I will endeavour to lap off. As I mentioned above, Terry Martini-Yates thinks it's pretty worn and says these heads weren't supposed to be re-lapped. He has spares so I haven't anything to lose by trying, and if I get it square at least I'll have a chance of setting it up vertically.

Is there anything else in the tape path that can affect the alignment? Should I measure where the reels are off the deck, as the hubs have grub screws that presumably mean they can be moved up and down the spindles a certain amount for adjustment.
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Old 21st Mar 2019, 7:34 pm   #69
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Default Re: Ferrograph 4A: Restoration advice needed

I can't advise specifically for your machine regarding mechanical adjustments because I've not worked on one that I can recall, all I can say is that the tape path should be all in order for proper recording and playback, the manual only seems to give one adjustment and that's for azimuth, I don't know if the height of the tape guides is adjustable or if head height and zenith are adjustable.

I can only say make sure that the tape path is in good order and that there is no tape curl at the guides etc, the guides should be parallel to the vertical face of the heads, anything different can cause uneven head wear, I used to service a lot of Sony reel to reel tape decks back in the day, the erase head was usually fixed (non adjustable) but the record/playback head(s) were fully adjustable for head height, zenith and azimuth, the input tape guide (the one to the left of the erase head) was usually adjusted so that the erase head segment was protruding above the top of the tape by the specified amount, once that was set correctly the height of the record/playback head segment could be adjusted to the specified distance below the top of the tape.

Lawrence.
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Old 26th Mar 2019, 1:08 am   #70
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Default Re: Ferrograph 4A: Restoration advice needed

The tape guides are threaded polished rods, so they sit through holes in the plate until the threaded shoulder is pulled up against the plate by the nut below. It doesn't look like there's any adjustment unless washers are used. I'll eye it along and see what's what.

I'm confused by the auto-stop and apparently my lack of it. The switch shown in the manual is much larger than my block, which is just two contacts with no switch mechanism.

There's a mention that the erase head is also an auto-stop switch, but that relies on a pressure arm that differs from the one I have by consisting of a moulded L-shape that slips into the erase head when not prevented from doing so by tape. There doesn't seem to be any connection for this to do anything on my erase head, so it could just be that the arm is allowed to travel when the tape end passes by, and that movement trips the switch that should be under the plate.

Attached are pictures of what I have in place of the switch, and what the manual shows (bottom middle of the 'underside' picture; labelled).
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Old 26th Mar 2019, 1:26 pm   #71
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Default Re: Ferrograph 4A: Restoration advice needed

Hi Uncle B,

There appears to be a loop of wire and moving contact missing from your auto stop. It is designed to make contact with the fixed contact on the bakelite body of the switch. The moving contact must be insulated from the peg and spring and that is why there is a sleeve over the peg.

Here is the arrangement on a Series 4 Vortexion, the sleeve on this one is black plastic. Watch out though, these contacts are all at HT voltage on these models!

Hope this helps,
Bill
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Old 26th Mar 2019, 2:28 pm   #72
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Default Re: Ferrograph 4A: Restoration advice needed

Setting the azimuth should be child's play compared to head tilt (which if wrong, over time causes the keystoning wear pattern). But as already mentioned, if there's already a definite wear groove and we havent relapped the wear groove out, there's not much choice but to reinstall the head exactly as it was, with the tape sitting neatly in the existing wear groove. For that is the only setting which will allow the best tape to head contact in that circumstance. Once we try and adjust the head azimuth with the wear groove unremoved, the tape may fight against the changed groove angle and may even pop out of the wear groove altogether. At worst, the tape is permanently damaged.

I specialise in transferring existing old tape recordings where play head azimuth is no longer fixed. It's whatever the old recording dictates. So azimuth becomes a tape by tape proposition and of course the play head must not have a wear groove.
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Old 4th Apr 2019, 3:05 pm   #73
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Default Re: Ferrograph 4A: Restoration advice needed

Thanks all. I've discovered that the noise I was hearing during testing tape playback was because the two tape guides before and after the heads were at the wrong height. They consist of a couple of threaded shaped end caps which can be screwed up and down relative to the top plate with a brass bushing in between. The tape was rubbing too much on the top or bottom of this.

I've decided the left-hand motor spindle is too high, so the guide was pulling it down. I wondered why there were some washers under the motor standoffs, and now I think that they were for setting the height of the tape from the top plate. I'll put them back in...

BillDWVA - that's perfect, thank you! It looks like this is is a modification I need to do. The switch in the manual must be a more complicated later version. Does your Vortexion have the L-shaped pressure pad or a felt one?

TIMTAPE - I think re-lapping is next, and then I'll have to struggle with head tilt. The head sits over a rod to allow it to rock sideways, but is connected by four screws. Thus it's possible to overtighten them and bend the base over the rod, affecting the forward/back alignment. This is what's happened with mine and become obvious when I was reassembling it, so I'll have to flatten the base in order to have a, err, baseline. I don't suppose there's any easy way to check for squareness against the top-plate.
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Old 4th Apr 2019, 3:34 pm   #74
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Default Re: Ferrograph 4A: Restoration advice needed

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I don't suppose there's any easy way to check for squareness against the top-plate.
When I worked for Sony I used to use an engineered 90 degree block as a guide for the zenith adjustment, it was designed to go right up to the head surface provided there was room on the deck plate for it to sit on. In cases where that wasn't possible I used the reflected light trick as per this Sony manual (last para in manual page 28 and the drawing in manual page 29):

https://elektrotanya.com/sony_tc366_.../download.html

Lawrence.
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Old 6th Apr 2019, 8:25 pm   #75
Uncle Bulgaria
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Default Re: Ferrograph 4A: Restoration advice needed

Once again you come up trumps, Lawrence. It's much appreciated.

I've been looking through TIMTAPE's lapping manual and am sourcing the recommended lapping films. Before then I'll have a go with the fine wet and dry stage, then try that clever light technique.

Am I reading it right in that the tape is just touching the head, so the light on the back of the tape is reflecting whether the bottom or top of the head is touching it more heavily?

My brother also has a workshop so may be inveigled into making me an engineered block.
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Old 6th Apr 2019, 9:06 pm   #76
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Once again you come up trumps, Lawrence. It's much appreciated.

I've been looking through TIMTAPE's lapping manual and am sourcing the recommended lapping films. Before then I'll have a go with the fine wet and dry stage, then try that clever light technique.

Am I reading it right in that the tape is just touching the head, so the light on the back of the tape is reflecting whether the bottom or top of the head is touching it more heavily?

My brother also has a workshop so may be inveigled into making me an engineered block.
Yes, that's about it, reduced tension for the reflected light trick, not sure if it will work on your Ferrograph but it might be worth a shot, nothing to lose.

I mainly used an engineered block, I have a feeling it came direct from the Sony factory as we had a close connection with them, I met one of the founders of Sony when I worked for them, Akio Morita, nice man, my boss at the main depot and sales office I worked at was Joseph H. Cohen, another nice man, he was one of the founders of Gendis (General Distributors) amongst other things Gendis took on Sony products and did a lot to promote the Sony name, some models of Sony transistor radios carried the Gendis logo (Google Sony Gendis)

Lawrence.
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Old 21st Apr 2019, 6:24 pm   #77
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Default Re: Ferrograph 4A: Restoration advice needed

The head has been lapped. No head gap is visible and the surface is a lot more even than it was. I've flattened the base of the head and adjusted the height of the motor spindles. Now to set the orientation.
  • At least one of the guides' brass tubes seems slightly smaller than the tape. Cut another?
  • To set the bias for recording, I presumably need a 'type' of tape. Is this best to be a new, current type or is there a 'generic' bias that will do for the varied secondhand tapes I have? Should I do it for 'Ferrotape'?
  • Hum appears to be less than the level the manual specifies (measuring VRMS across the 'speaker) but it still audible. A feature of the machine?
  • The bass control appears to do not very much. Could this be because the electrolytic capacitors C9/11/12/13 have gone off? I've replaced the others associated with the 'equalisation' module.
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Old 2nd May 2019, 2:17 am   #78
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Default Re: Ferrograph 4A: Restoration advice needed

Any thoughts on the previous issues?

Another one for you Ferrograph owners - are the reels supposed to be parallel to the deck?

I've been adjusting the spindle levels and have noticed that both are slightly tilted towards the front, so the points on the circumference of the reels closest to the operator are closest to the top plate. Is this a feature or should the reels be parallel to the top plate?
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Old 2nd May 2019, 10:28 am   #79
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are the reels supposed to be parallel to the deck?
Yes. You can adjust the shaft tilt by the three tensioned mounting screws of the spooling motors.
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Old 5th May 2019, 4:59 pm   #80
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Yes. You can adjust the shaft tilt by the three tensioned mounting screws of the spooling motors.
On mine the screws are not tensioned, except by the weight of the motors hanging off them when the machine is lying down. The screws each thread into hex standoffs that butt up against the top plate, and have their other end connected to the long hex screws that hold the rotor bearings and motor assembly together.

The standoffs are all the same length, so adding washers as shims seems the only option. From the quality of the rest of the machine, this lack of precision seems unlikely!
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