Ferrograph Re-capping

[DMcMahon]

From your spares listing can you identify the switch part number ?

I have a spares Series 7 machine, am wondering if it might use the same switch.

David

[untune87]

Thanks David! It looks fairly big, open and simple as the contacts are just strips that are pulled into place by operation of the lever on the deck, doesn't look like it would be too difficult to add and remove parts.

The manual lists it as SW3, "Motor Switch" and part no. MC/2959

[untune87]

Picture of the culprit for reference

[DMcMahon]

Apart from the previous part number pages you attached, I cannot find a Service manual for the 633. I did find a manual for the 631 which I assume is similar and it lists "SW3 Selector Switch" as MC/1755.

Equivalent switch on my Series 7 is "SW100 Function switch" with part number 750-000 so does not sound like the same part. It is 4 position and 4 poles I think, will try and have a look at mine a little later.

David

[untune87]

Originally Posted by DMcMahon

Apart from the previous part number pages you attached, I cannot find a Service manual for the 633. I did find a manual for the 631 which I assume is similar and it lists "SW3 Selector Switch" as MC/1755.

Equivalent switch on my Series 7 is "SW100 Function switch" with part number 750-000 so does not sound like the same part. It is 4 position and 4 poles I think, will try and have a look at mine a little later.

David

No problem, thanks for looking! I actually have the original manual complete with all the original test certificates (including the correct voltages, biasing etc for this unit) that were given to me by the original owner. He also apparently collected a lot of magazine clippings, reviews etc from 1967 about it. I may try to digitise these along with the rest of the manual at some point - I don't have a scanner anymore, but pictures on the phone are fine for now!

At the moment I'm just pleased that the problem is a relatively simple fix and the issue is not (at least at this point) the transformer or motors. I have been busy with other distractions today but hopefully I'll get a chance tomorrow to remove the switch and get a proper look at it - and I'm condfident that, given how many of these decks have probably been gutted for their valve amps, there must be spares out there somewhere. And, from what I can tell, it looks like the switch is a relatively simple affair; the only fault is a brass strip that can be unscrewed and replaced.

[DMcMahon]

Originally Posted by DMcMahon

Apart from the previous part number pages you attached, I cannot find a Service manual for the 633. I did find a manual for the 631 which I assume is similar and it lists "SW3 Selector Switch" as MC/1755.

Equivalent switch on my Series 7 is "SW100 Function switch" with part number 750-000 so does not sound like the same part. It is 4 position and 4 poles I think, will try and have a look at mine a little later.

David

I picked up the incorrect switch above. The equivalent switch on my Series 7 is SW102 "Start switch (Motors)" part number 748-000 but this looks like a single switch. Same part number also for SW103 "Start switch (Economy)", SW106 "Run switch" and SW107 "Record switch (Oscillator)". I will check this switch out shortly.

David

[DMcMahon]

Checked out my switches on my Series 7, they are just standard microswitches actuated by heads of screws or sprung arms etc.

So unfortunately no good for your switch.

David

[untune87]

Hi David,

No problem at all, I really appreciate you taking the time to look.

I've been a bit tied up today but I had a bit of time to get the switch away from the deck and inspect it. It looks like it's two identical switches glued together, but after looking closer I can see that BOTH the strips are starting to fail at the same point. This reinforces the diagnosis of the switch being the cause of the motor issue as I noticed the last time I ran the deck there seemed to be an intermittent behaviour in the capstan motor, whereby it didn't appear to be running at full capacity, and the capstan wasn't taking as long as it should to spin down when disengaged.

I have attached a picture for reference in case anyone has similar problems with theirs. And as you can see from the image, the brass pieces can be unscrewed and removed/replaced, therefore if I can't find a donor switch then I could always make something using some thin brass sheet or similar.

[Station X]

The difficulty in making new strips might be that they have "pip" type contacts made of another material.

It should be possible to solder a piece of brass across the gap.

[untune87]

Originally Posted by Station X

The difficulty in making new strips might be that they have "pip" type contacts made of another material.

It should be possible to solder a piece of brass across the gap.

Very true, pic attached showing the contact 'pip', the other strip snapped when I tried to remove it. The other is intact enough for measuring rough angles, though from the way it operates I doubt accuracy is paramount

Wouldn't be too difficult to put perhaps a very small screw through, reinforce with solder. Probably easier to source a replacement but still not outside the realm of possibility!

[flywheel]

Originally Posted by untune87

Very true, pic attached showing the contact 'pip', the other strip snapped when I tried to remove it. The other is intact enough for measuring rough angles, though from the way it operates I doubt accuracy is paramount

Wouldn't be too difficult to put perhaps a very small screw through, reinforce with solder. Probably easier to source a replacement but still not outside the realm of possibility!

Hi, I can post you a couple of these switches if you DM me an address (reclaimed from old machines I broke up because of otherwise poor condition).

[untune87]

Last night I decided to attempt a repair, after finding some thin brass contact material from another old torn down tape deck. It was thin enough that I could put a slight bend in it, to keep the angle of the original. Fixing the cracked one was easy enough; the one that had broken into two pieces however was incredibly fiddly as it would keep moving and was difficult to keep still. I got it in the end - not the prettiest, but solid enough to hold.

Getting the switch back onto the deck was incredibly stressful! One of those jobs that you need six pairs of hands for. The brittle plastic of the switch snapped at one point, washers and nuts fell and got lost multiple times, and there was no room to get fingers or tools in at a clear angle. Eventually managed to secure it and I'm happy to report that everything now functions as it should! Motors are running correctly and the solenoid is holding without any issue.

Only thing left to test is tape record and playback, but the tape path needs a good clean first just in case. I'm not sure if the repaired contacts will hold (they seems sturdy enough) so I'm still getting hold of replacements just to be on the safe side so that if it goes again, I'll have a spare.