Ferrograph Series 7 Model Number Identification

[DMcMahon]

Originally Posted by Ted Kendall

Around 1970, in Studio Sound, Ferrograph ran a series of adverts showing Sevens in various professional situations - the Moon landing, Radio London and I think on a submarine - could have been a surface ship - Naval anyway.

Maybe the Naval one Ted referred to is attached.

[Ted Kendall]

Yup, that's the one.

[flywheel]

Originally Posted by Ted Kendall

The whole problem with the originals was that they were polyurethane - in common with Chilton, Ferrograph went for this "wonder" material and came a cropper, as did Ampex eventually when their polyurethane binders turned to goo. Fortunately, the chemistry is now better understood, and modern supplies should be OK.

That's very interesting - I'd been led to believe years ago that the problem was poorly cured or formulated neoprene from a new supplier (I even wrote something on that basis for a web site I had around 2004 which was copied by others!), but this explanation makes more sense.

[DMcMahon]

Removed the 6 idler wheels from both units and cleaned up the gooey mess, took some cleaning especially on the incomplete unit. I was going to throw the idler wheels away but decided to keep and some time later I will clean off all the horrible decomposed rubber and just keep them just in case some time in the future need to get new ones made and need the metal cores.

Fitted the replacement Series 5 idler wheels, had some fun with the idler arms with the springs on their ends kept unhooking themselves while trying to refit the arms !

Removed the PSU, found that the adrift component is not a capacitor, not quite sure yet what it is, a transformer or inductor ?? it has come out of its mounting clamp, to get to the clamp tightening screw I need to remove/loosen a large capacitor.

Tried to hardwire a mains power cable but access was so tight to the relevant connections, decided it would be easier to pull out the Cannon mains plug, but it was not easy.

The 2 small screws securing the connector were so tight due to the nuts having been seriously locktited, managed to remove one screw but could not budge the other one and only ended up damaging the Philips headed screw.

Could not find my drill to drill out the screw so attempted to break the screw off by levering the connector body, but you guessed it, the connector body broke instead, so that connector is in the dustbin. Now am going to fit a mini Bulgin mains connector.

If I can find the correct/compatible Cannon female mains cable connector, then later on I may remove the Cannon connector off the incomplete unit and refit it in place of the Bulgin.

For reference the Cannon mains plug # is XLR-LNE-32

[llama]

That loose device looks like a transformer - possibly for balanced audio in/out. Or maybe a step-up transformer for a mic input, depending on where it is in the circuit.
Graham

[DMcMahon]

Hi Graham,

Thank you, I do intend to check out its wiring connections. There looks like there maybe another 2 similar ones in the PSU. There are also two 4 pin connectors (maybe only 2 wires wired on each), which like the transformers I cannot easily see in the schematics.

I wonder if they are part of the BBC modifications ?

David

[DMcMahon]

Originally Posted by Ferrograph723

Are the holes in the reel tables not there just to hold the 3 rubber inserts in place? The photos look like the inserts are missing in the complete one, but are present in the incomplete one?

Mine has the inserts, and has the extra tape pillar/guide and has a black head flap (so it's a Mark 2?) - but it has round head cans! But then my model number is 723 which I can't find any record of ever having existed, so who knows what is should or shouldn't have!

Does anybody know how the rubber inserts are held in place, are they glued ?
they seem pretty secure in my incomplete unit

[Mistral13]

The following shows a 'Y722' variant, with isolating transformers:

Please see attachment

[DMcMahon]

That is really good, I have now seen that there are 4 transformers which agrees with your document.

Which Series 7 document is this from ? I cannot see it in the standard Series 7 User and Service manuals or Mk. 2 User manual.

A previous post indicated that the Y prefix was a Military indication, so maybe the impedance/matching and/or isolation transformers are a Military modification as against a BBC modification.

Having said the above, my incomplete unit appears to have the same 4 transformer modification and it has a BBC label with a P Prefix.

[Mistral13]

The transformer setup is taken from the Y722 service manual. Luckily it is just under 4Mb so I can attach it to this msg - please see below


David

[flywheel]

Originally Posted by DMcMahon

Hi Graham,

Thank you, I do intend to check out its wiring connections. There looks like there maybe another 2 similar ones in the PSU. There are also two 4 pin connectors (maybe only 2 wires wired on each), which like the transformers I cannot easily see in the schematics.

I wonder if they are part of the BBC modifications ?

David

Those brassy-looking mumetal-cased objects are Ferrograph original balanced to unbalanced transformers (check out the spivs on eBay selling their higher-ratio valve deck equivalents as 'Partridge' moving coil cartridge transformers for £100s!). Why one of them seems to be floating free, though, is puzzling.
The only real BBC mod is likely to be the power connector.

[DMcMahon]

Thank you Mistral13, that is fantastic ! I did not even know that version of the manual existed. Now I can see it on at least a couple of websites.

A shame that the circuit diagrams Figures 26-28 (listed in its List of Illustrations) are missing from the document, I was hoping that they might be there and not cut up (size wise) like the standard manual versions.

The photos of the Power Supply in the Y722 manual just show the standard Power Supply without the transformer modifications.

Once again thank you very much.

David

[DMcMahon]

Andrew,

The transformer has just come out (worked loose I assume) of its clamping holder ring, I am just about to refit it, will do a photo a little later where it will become clear.

David

[DMcMahon]

Those brassy-looking mumetal-cased objects are Ferrograph original balanced to unbalanced transformers (check out the spivs on eBay selling their higher-ratio valve deck equivalents as 'Partridge' moving coil cartridge transformers for £100s!). Why one of them seems to be floating free, though, is puzzling.
The only real BBC mod is likely to be the power connector.[/QUOTE]

Wow ! I see what you mean, maybe I should be removing all the transformers and putting them on eBay

[DMcMahon]

Refitted the adrift transformer all OK.

[DMcMahon]

Originally Posted by DMcMahon

Thank you Mistral13, that is fantastic ! I did not even know that version of the manual existed. Now I can see it on at least a couple of websites.

A shame that the circuit diagrams Figures 26-28 (listed in its List of Illustrations) are missing from the document, I was hoping that they might be there and not cut up (size wise) like the standard manual versions.

The photos of the Power Supply in the Y722 manual just show the standard Power Supply without the transformer modifications.

Once again thank you very much.

David

Have now found the Y722 Operators Handbook, at the end of which is the schematics, these show the Line I/P transformers but not the 600 ohm O/P transformers.

Like the standard service manual the schematics are cut up into sections with some duplication's, which I find very messy to looks at.

[DMcMahon]

Fitted and wired mini Bulgin mains power plug in place of broken Cannon. The live and neutral wires were very tight so replaced the live wire from the fuse and for the neutral wire (not so easy to replace) gained a few mm by relocating the wire the other side of a cable loom P clip it went through.

Replaced the PSU 2A mains fuse with correct 1A fuse.

Tested the PSU (out of machine) the 50 volt output at C700 was around 51 volts with 0.5 volt 100Hz mains ripple. The 24 volt output at C701 was around 28 volts with no real measurable mains ripple.

Don't think the 24 volts has any load on it until PSU connected back into machine, the 50 volts has some load (power amps).

To test the PSU out of machine you have to put 2 links in SK101 to simulate the mains on/off switch, namely pins 4 to 8 for the live and pins 3 to 6 for the neutral.

Will refit the PSU back into machine after a little more cleaning of the machine.

Have ordered a new Pinch Wheel/Roller.

Any ideas about "LRTU" on the PSU, I assume it is an abbreviation, something like "something something Technical/Training/Teaching Unit" maybe ?

[Ted Kendall]

Local Radio Training Unit? - Sevens were used in local radio more or less from the start.

[DMcMahon]

Originally Posted by Ferrograph723

Interesting that the 'complete' one has a silver head flap/cover. Most Series Seven's that I've seen have a black flap.

Also mine has an extra tape guide on the left hand side, just to the right of the small black circle (which is the reel height adjuster). This is part of the auto-stop foil detector (which detects a short between this guide and the tensioner just to the left of the heads - I assumed all S7 had these fitted?

I wonder if that is another BBC specific mod - i.e. no auto-stop fitted?

The plate/panel does not have a cutout for the extra tape guide, maybe this means my particular revision of Series 7 was not built with the tape guide/auto stop detector ?

[DMcMahon]

Is there any history of Electrolytic/Paper capacitor failures on the Series 7 ?