There are 3 N channel FETs in the D 61. ( mnfg. Spec)

p/n 151 1076 00
or 151 1076 01.

Years ago I used a MPF 102 to replace one of them. However I am using these scopes
again ( 11 of them) and wonder what the spec is or if they are just a hand selected generic?

Two of them are the impedance converter in the vert front end, and the other is in
the time base.

Ant Telequipment techs out there from 1974 ?

Wel, the Sphere site ( http://www.sphere.bc.ca/test/tekequiv.html ) wasn't much help. Is this a dual FET? If so, using two MPF102s might not be the best idea. Dual FETs are usually used so that the balance doesn't go haywire with temperature changes as well as having matched components. Dual FETs are almost always used on the front ends of preamps.

No, single, one as the input transistor for Ch.1 and Ch.2

It's a source follower circuit. I'd think that any FET that can handle the circuit conditions and is fast enough will do just fine. No gain here, capacitances might be the only issue but support components are low value so it's no big deal.

D61 is a Telequipment, but just in this time it was build, Tek have buyed the company

151 1076 00 is a Tek spare part number.

greetings
Martin

Thanks for the replies. The scopes were made in 1974, and I'll look into the TEK spare.

They are a very old, very ornery, scope, but when they work, they work quite well.

This is much to the annoyance of modern learners expecting their electronics to work
with complete obedience and offer up help in setting the controls.

Its a DC scope with limited bandwidth so I think they chose that transistor in each
channel to at least drift in the same direction, otherwise the traces would move apart.
perhaps why they had two part numbers listed for each.

I have a Heathkit curve tracer that can AB two sockets, so I can see if MPF 102s will look
the same.

Ah, yes...

My Tek cross reference says 151-1076-00 is a WN537, and the -01 is a WN537B Obviously, both are FET, N-Channel.

Not certain that's going to be of much help tho.....

David

I'll keep looking. Dean Huster mentioned Sphere Electronics right here in British Columbia. I didn't
see anything.

I went through the scopes Friday and found two that worked well, and took them to a class
I was teaching on Saturday. This first scope twinked out after an hour, however the second one
ran OK.

Getting them all up is going to be a big job, but they are ultra easy to work on, have excellent
diagrams, and do not use any ICs at all.

They are a 10 mHz dual channel scope meant to fill the TV service market at a reasonable cost.

They they employ many trimpots, and are rough-hewn out common parts that are fine
sculpted by adjustment.

Just looking at Sphere's web page, CRTs particularly small electrostatics, new and used seem to
have a good market. Just the CRT's in these scopes, the ones with reasonable emission, along
with the case, mu-metal shield, and power transformer section might fetch some coin.

Good luck. You must be used to working on a different Telequipment than I am... I've a D65 in the basement I _hated_ working on. So much so that I gave up on it. (The timebase wasn't running) Couldn't get to the backside of the board unless you removed the TB switch, and disconnected a couple of dozen wires, running to various locations.

The manual wasn't great either. (Once I purchased one.) I would of liked more waveform diagrams, and/or voltage measurements on the schematics...

Meh, hated the thing, so much so, that I still haven't (and probably won't) ever try again at fixing the thing. The last time I did remove everything, and replace a few components, and put it back together it was worse. Anyone want some D65 parts?

David

The manual for this one is minimal, but has 11 schematics with waveforms and a double page
foldout for the pcb.

The case is sturdy and attractive, but the frame is pop-riveted together. Major pain in the
butt areas are the front panel controls. All in all, it is assembled like a Heathkit, and could
easily be repaired by a TV tech in the 70's .

I bought them for maybe 40 bucks each from U.B.C. SERF in 1990. Each had its manual.
They were used by me for about 12 years and stood up well. I stopped using them when
I got a set of Heathkit 9720s. Those have all crapped out (power switch) gummed up.

The CRT is a GEC 1324 Y but may be 1346 Y. (never had one out and the graticule is green)