Marconi TF2650 FET meter

[beamcurrent]

Part of my enthusiasm for the said box of meters, in the previous post, was this fellow. I have a soft spot for Marconi kit so I now have the TF2650.

Predictably it does not work. It has grown a small piece veroboard near the input terminals. This board has a socket for and IC, but no IC. I think this was a bodge to get round a dead and hard to replace input FET.  

Does anyone have any knowledge of this meter and possibly a circuit?

   

Regards

Brian

[Stockden]

Hello Brian,

I can help with manuals and circuits (there appear to be more than one version of this meter). If you let me have your email address I'll happily send them to you.

I too have a non-working TF2650 but in the traditional way haven't got round to it yet..

Regards,
Hugh

[AlanBeckett]

Joe will put it in the Archive if you send him a copy.

Alan

[Yorkie]

There appears to be two versions  of this meter - one is branded the Conway 'Masteranger' multimeter (model 639),  made by Meratronnik in Poland.

The 32-page manual is attached.

Maybe Joe could pop it in the Archive?

[Stockden]

I've just sent an assortment of files to Brian and I'll contact Joe to see if he'd like them for the archive. Since the design was, I believe, originally Polish (though badged by others including Marconi) some of them are actually in Polish. Fortunately you don't need to be able to read the language to understand the diagrams, board layouts or component lists

Hugh

[beamcurrent]

Thanks very much to Hugh and "Yorkie" for providing the circuit. My meter has a made in Poland sticker and is serial number 9600.

The layout seems to correspond to the circuit version with the op-amp, HLY7006R. As I said the original op-amp has gone and a small veroboard with an empty IC socket is fitted in it's place.

A DuckDuckgo search produced a link for a Conway brochure
http://www.schematicsforfree.com/archive...uipment%20&%20Measurement/Meters/Conway%20639%20Masteranger%20Brochure.pdf

Brian

[ppppenguin]

That brochure says the meter is ideal for use in various fields including Computery [sic]

[Yorkie]

The circuit is quite poor resolution, but the IC is an HLY7006R, long since obsolete, so if that's what's missing, it looks like it's jiggered.

From what I can glean, mainly from Polish enthusiasts,  the IC can't be sourced. (A search hasn't provided any useful links).

I'd forgotten that any member can add posts to the Archive - it's just that when added, we can't then add other posts to that thread, because it is of course and archive and any discussions can take place in the appropriate section, as here for example. Hence, I've popped the manual in the archive myself, rather than to expect Joe to perform my chores!.

[Nick]

It used an HLY7006R IC, long since obsolete and now, 'unobtanium'.

Actually, the HLY7006R is a pretty straightforward hybrid which can be easily replicated from standard parts:

   

[Yorkie]

That's well spotted Nick - should give Brian some hope for a working meter. Would fit on a small piece of Vero or even a little PCB.

What type of diode would be needed - the one mentioned on the circuit looks obscure : 'BAYP795'?