Telequipment D66A

[joebog1]

This morning I picked up a Telequipment D66A for $50 (about 30 quid). It's in excellent order, but is missing the power cord (see parts wanted ad).

I have ordered the circuit diagram and am waiting for the download.

I was wondering if anybody here has one or uses one. The particular unit I have scored seems to have a department of education plant number engraved, and does not have any dust anywhere inside the cabinet. I have been working on electronics for enough years to be able to recognise when an old and well worn unit has been blown out with compressed air, and this unit does not have those tell tale signs. It's meticulously clean inside, and all the little paper labels from production are all still there and quite readable.

Any comments about this CRO, anybody?

Thanks in advance, Joe.

[MotorBikeLes]

Very nice scopes. Single timebase I think, unlike the D67 which has a dual T/B. Bandwidth probably 25MHz.
The power cord is rare, very obsolete, and some of them go rotten with age (the old hydrochloric acid released from PVC. Best thing to do is remove the socket and make a small plate with hole for a cable restraint. I have done a few.
There is supposed to be a plastic cover over the voltage selector area, as "lives" are accessible to silly fingers. This was a safety retrofit.
Inside, the mains fuse holder is handily placed for giving you a belt. I always find a plastic tube or similar to fix over it to keep the volts well away from me.
Les.

Mods, is "Hydrochloric" marked red by MY spellchecker as I type, or that of the site? I assume it is a US version, and I thought I had "UKed" mine.

[AC/HL]

Mine underlines misspelt words with a red wiggly line, but I think it uses your browser's dictionary and settings, which may be an add-on or plug-in.

[joebog1]

Thanks Les.

I still hope to find something as this little CRO is in excellent order. Its best feature is that it is analogue!!! I have some digital CRO's complete with their switchmode power supply hash visible on the trace. One never knows if it's the CRO power supply or a noisy amplifier. A little like why I use my AVO 8, instead of my Fluke digital. Do I even care if it's 456.2354 or 260 approximately, volts. A glance from the corner of my eye shows a needle "about" midscale. My eyes won't register the 3.7646 "wrong" voltage anyway.

Joe

[WME_bill]

Telequipment D65/D66/67.
A family of very nice scopes. I endorse what MotorbikeLes says about them.
The D65 uses a spiral pda tube for 15Mhz, single Time Base. Your D66 is 25 Mhz, using a more sensitive brighter mesh tube, and the D67 is the dual TB version of the D66.
All models use commodity transistors, with no specialist integrated circuits, so are easy to repair even now, 45 years after they were made. A few transistors are marked with special Telequipment numbers, but the commercial equivalents / substitutes are known.
I still prefer an analogue scope to digital, and my Avo to a Digital voltmeter. They seem to give a quicker response when fault finding, when the exact reading is of less importance than a general existence of a signal or voltage. Most circuits will operate within 10% of the design levels, and you only need to know to within 100mv when finally adjusting to specification perfection. Except when checking forward conduction on a diode or transistor, as then you need 100mv, and is about the only time I use a DVM.
The power plug is unique to Telequipment, made by Belling Lee. Your best option is to change to a fixed cable. Fitting the usual RS IEC320 chassis plug means cutting a larger hole in the chassis. The fixing holes slightly overlap those of the previous Belling Lee socket, so have to be filed out, as a drill drifts into the old hole or breaks.
I have the complete manuals for these models if you want it.
My Firefox protests at Hydrochloric acid, so I have added it to the dictionary. It only recognises hydroelectric. The standard Firefox is set to English-US.
But it wants a Z, not an S in recogniSes. Even Fowler rather sits on the fence with that one, though with one leg definitely on the S side.
wme_bill.

[Andrewausfa]

I have a D65 which, after Les gave me some advice on a few years ago to reflow the little solder tunnels from front to rear on the pcbs, has worked perfectly ever since. One of the large electrolytics on the RHS had leaked, hard to see, so may be worth checking yours though from your post above yours seems low hours.

Nice scopes though and one I'll likely not get rid of.

Andrew

[AC/HL]

Tools - Add-ons - Dictionaries, search for British English.
It will then accept UK spelling without trying to re-educate you.

[WME_bill]

Telequipment D65/66/67. and Languages.
Thanks to AC/HL for tip about Firefox UK English. It works.
wme_bill

[MotorBikeLes]

Yes, I had forgotten, D65/66 will likely have similar PCBs to D67, and on that design of circuit board, feed through holes can develop hidden "drys". Special techniques needed. Either poke a thin length of wire through and ensure the END of the wire is soldered on each side, or (my method), use your soldering iron to "boil" the solder for a few seconds. You will "blow" a bubble which bursts, remove heat. Carefully ensure the component which passes through the hole is soldered on one side, leaving the other side unsoldered. Back to the non-component side, and solder that fully, but do it QUICKLY. You now have a joint that WELL NOT fail tomorrow, next tear, or in 10 years time.

Hydrochloric acid. Just ensured my spell checker is Eng-GB (it was Eng-US), but still underlined with wiggly red line. Maybe I need to restart firefox. Will try again another time.
Les

[joebog1]

It seems the mains lead connector is no longer available, so I am looking at fitting an IEC mains socket.
My pic entitled "only space" shows inside the chassis, and its the only available space on the back panel. Its right behind the serial number, and I am loath to destroy that. So I will probably follow the previous suggestion, of hard wiring the mains cable in through a cable clamp.
Pic " pregnant vent" is self explanatory, being one of the low voltage caps in the power supply. "HV cap" is one of the high voltage caps, and the plastic sleeve is shrinking. I dont know if that is from the original solder job, or its been hot. Pic of the ultor shows no dust buildup, or even any trace of buildup.
Inside the chassis is spotless, so I still think its very low hours. All the control knobs are still very "sharp" on the flutes,whereas on my other CRO's that I use all the time, have been worn down so that the flutes are not so sharp.

I will run it up first on a variac, while watching the ammeter on the mains input side. The specifications states 50 watts consumption ( approx) so I will be watching the ammeter for any excess currents. 50/250=.2 amps, on a moving iron ammeter.

Any other suggestions that are offered would be appreciated, as I dont want to damage this fine tool. I have never owned a Tektronix/Teletronics CRO, or any other test equipment made by them. I have used them of course, at various establishments that I have worked for in the past.
I do have a poor condition S51B, but its in such poor condition I have not attempted to get it going.

Thanks in advance

Joe

[Andrewausfa]

Joe,

All of the HV ones on my D65 looked like that, I suspect if it were long term heating that shrink wrap on the capacitor next to that chunky grey resistor would have suffered first. It had also been hard wired before I got it so I just replaced the mains cable.

Andrew

[CambridgeWorks]

Joe, are you going down this modification route, as I did reply to your wanted post as I think I have a lead, just needs finding.
Rob

[MotorBikeLes]

I was out in the shed this afternoon grinding a lathe tool, abd sitting on top of my stock of HSS was a little card with the details I wrote out decades ago for the mains lead replacement. blindingly simple, but the dimensons do work . NOT to Scale.
Les.

[joebog1]

Thanks Les.

Looks just the thing!! Will post pics of this mod when fitted.

Joe

[joebog1]

Thanks Andrewausfa.

That is very reassuring indeed. In fact the red heatshrink on your high voltage caps looks worse than mine!! I won't worry about it for the time being.

Best regards, Joe.