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Old 9th Jan 2011, 6:09 pm   #1
AlanC
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Default Telequipment D34

Hi All

I seem to be attracting 'scopes at the moment- having sorted my S32A I've become the proud owner of a Telequipment D34: a lovely little solid state portable dual-beam instrument with built in Ni-Cd battery. The previous owner said it hadn't been powered up for ten years, so I checked the mains psu for safety (it was fine) and then decided to see what state the Ni-Cd cells were in- they're D size cells, 6 of them. Amazingly, all bar one came up almost straight away; and the recalcitrant one seems to have responded to being zapped with a few amps followed by a steady charge.

The 'scope works bar two faults that I've found so far- the brightness control is powerfully intermittent, although it seems to be getting better with use. The trace fades out unless you sort of hold the knob downwards...

Also, the timebase doesn't work properly on all time/cm ranges which again is probably the switch needing a clean.

It's beautifully made with boards that hinge out for service, and obviously was built with top-quality components.

Does anyone either have, or know where I can get a circuit diagram from?

Cheers, Alan
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Old 9th Jan 2011, 7:56 pm   #2
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Default Re: Telequipment D34

Not sure if this will help.

Daniel.
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Old 9th Jan 2011, 8:17 pm   #3
Alan Stepney
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Default Re: Telequipment D34

I have one of those on my bench right now.
I use it for the "everyday" tasks, keeping the bigger and heavier ones under the bench until needed.
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Old 9th Jan 2011, 10:32 pm   #4
Alistair D
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Default Re: Telequipment D34

I have both a D32 and a D34 here. The circuits are quite different. I know where the D34 manual should be. If I can find it tomorrow I will scan the schematic.

Al
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Old 10th Jan 2011, 7:53 am   #5
AlanC
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Default Re: Telequipment D34

Thanks Al, I would really appreciate that.

What's the significance of the left-hand LED flashing? I got the impresssion that it meant the battery was low while playing yesterday, but now it seems to do it if it's on charge from the internal PSU...

Cheers,
Alan
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Old 10th Jan 2011, 3:47 pm   #6
Alistair D
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Default Re: Telequipment D34

You are correct about the LED flashing. Has your dead cell died again?

I have a scrap D32 as well as the other 2, if your brightness pot does not respond to cleaning I can supply the one from the D32. As far as I can see it is the same part as used in the D34.

The schematic is 14 pages long. There are 2 more if your scope has the ext X and variable timebase options.

Here are the first 5. I will post more later.

Al
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File Type: pdf D34p2.pdf (409.8 KB, 466 views)
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Old 10th Jan 2011, 8:30 pm   #7
AlanC
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Default Re: Telequipment D34

That's fantastic Al, I'm really grateful. Umm, I wondered if I could get some cleaning fluid into the pot- I haven't examined it that closely yet; from the quick look yesterday it looks like the body of the pot is longer than normal; and mounted some way back from the panel. Thanks for your kind offer though- I'll let you know.

Re the duff cell, oh probably! I have enough experience of trying to rejuvenate old NiCds to know that there is little chance of them being any good after being bang flat for ten years. And they may have been well past it before this- they look original and the scope will be 1980's I guess. The cells develop some kind of internal short don't they and while you can blow these off you can't undo the basic fact that the cell is kn*ckered!! I would consider buying a new set of cells for this scope though, it really is a beauty.

The timebase fault isn't the switch I don't think. It is that it behaves normally on speeds below 1mS/div but on 1, 0.5, 0.2 and probably 0.1 mS/div you get a trace that starts bright at the left but dims as it goes across the screen- the bright bit goes further across on each speed above that- see the pics below. It seems fine on speeds above 0.1mS/div btw. This might have to do with the changeover between chop and alt modes (he speculated wildly) but that's why I needed the schematics...

Thanks again,
Alan
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Old 10th Jan 2011, 8:35 pm   #8
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Default Re: Telequipment D34

Hi Gents, I have one of these as well, a great little portable when it was working, but the voltage multiplier has died. Can anyone sell me a replacement?

Thanks, Ed
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Old 10th Jan 2011, 10:52 pm   #9
Alistair D
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Default Re: Telequipment D34

Ed:
The EHT arrangement on the D32 is made up of discrete components on the PCB rather than a module. Is the D34 module encapsulated? I can offer you the high voltage diodes and caps if you can rebuild the module.

Alan:
I will post more schematics tomorrow.

These days I tend to use IPA as a switch cleaner and only use one with lube if that fails. All of the preset pots are of the open type so dust builds up in them. I always have some switch cleaner for these as well.

Al
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Old 11th Jan 2011, 3:19 pm   #10
Alistair D
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Default Re: Telequipment D34

The rest of the schematic
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Old 11th Jan 2011, 9:21 pm   #11
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Default Re: Telequipment D34

Hi Al, yes it is an encapsulated module and it is going down where the PDA lead comes out.
It's quite tight for space, but I'm sure I can put something together.
PM me with costs and I'll get a cheque off to you.

Best regards, Ed
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Old 11th Jan 2011, 10:54 pm   #12
Alistair D
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Default Re: Telequipment D34

Ed.
While scanning the rest of the schematic I did some reading up on the Eht generator. As far as I can work out the D34 will need 12 diodes and capacitors. The donor D32 only has 4 of each(the EHT is much lower). You are welcome to these FOC if you still want them. Pm me with your details.

Al
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Old 21st Jun 2011, 10:31 pm   #13
electron22
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Default Re: Telequipment D34

Did you find out what that timebase problem with your D34 was? I have same model and same fault and switch cleaner is not doing any good. david
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Old 22nd Jun 2011, 6:37 pm   #14
AlanC
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Default Re: Telequipment D34

Hi David,

No, I never did. Due to my dad becoming ill and then passing away I put it (and almost all other projects) on the back burner...

Well you've ruled the switch itself out then I guess; interesting that yours has exactly the same fault though! What gets switched in (or out) between 1 and 0.1mS/div I wonder? The diagram that Alistair posted will surely point the way here.

One check I was going to carry out was to see if a waveform was displayed on the faulty ranges correctly even though it fades out. e.g. display a 1kHz waveform and see that the display really is one division. Because the timebase speed could be way, way out if the timing capacitor selected on those ranges (is it C4?) were open. Also the fading could be due to the sweep velocity speeding up as it goes i.e non-linearity of the timebase waveform and you'd easily see this. Mmmm- might have to dig it out at the weekend and have another look.

Fortunately I have another 'scope so can look at the waveforms.

Best regards,
Alan
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Old 22nd Jun 2011, 7:28 pm   #15
electron22
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Default Re: Telequipment D34

AlanC

Thanks for reply. My D34 seems to have started working correctly now all by itself. I left it running last night for a few hours. I will keep my fingers crossed that it stays that way. It might have been the switch cleaner taking time to kick in or it might have been me tapping things on the timebase PCB but my guess is maybe an electrolytic somewhere that has got better with some voltage on it. After all this scopes probably had a few years without use.
I bought two of these (D34 and D32) sold as faulty. The D32 needed a repair to a solder joint that a Ni-cad had leaked on and now works fine, and the circuits from this site helped lots.

david
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Old 22nd Jun 2011, 9:35 pm   #16
Alistair D
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Default Re: Telequipment D34

Before spending lots of time fault finding, it would be worth checking the unblanking amplifier settings. In particular the setting of R322.

The other problem areas that can cause all sorts of funnies are the three slide switches. Give them a liberal dose of switch cleaner.

Al
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Old 23rd Jun 2011, 1:22 am   #17
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Default Re: Telequipment D34

Alistair D,
Thankyou.
David
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Old 23rd Jun 2011, 10:43 am   #18
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Default Re: Telequipment D34

Hi,
reading this thread has encouraged me to look at the portable telequipment scope I have here somewhere. I did get as far as finding that the transistors in the inverter circuit had failed, and I did get some replacements.
regards Peter B
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Old 15th Mar 2014, 7:14 pm   #19
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Default Re: Telequipment D34

Hi Al,

I have a D34 which has following problems:

1. Inverter circuit - transistors found defective.
2. 10+2 voltage multiplier defective.
3. Ni-Cd needs replacement.

I have problem for item #2 i.e. 10+2 voltage multiplier circuit. You have mentioned in your message dated 12th Jan 2011 regarding diodes and capacitors.

Could you please tell me what make, value , type and ratings of each diode/ capacitors to be used?

Also what kind of insulation / potting compound do you suggest for the multiplier block.

Thanks
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Old 15th Mar 2014, 8:52 pm   #20
Ed_Dinning
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Default Re: Telequipment D34

Hi, I used ceramic 1000pF caps and 2000v diodes from one of the distributors (RS, Farnell). These are common and small components, They were assembled on perforated board (not tracked veroboard) with push fit pins. The whole assembly was then fitted into a small potting box and filled with paraffin wax. It has now been working well for the past 3 years.

Ed
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