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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders. |
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24th Jun 2018, 6:21 pm | #21 |
Nonode
Join Date: Dec 2012
Location: Kirk Michael, Isle of Man
Posts: 2,346
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Re: Telequipment D/S52
Well, it looks as if I was writing nonsense. I have bought and sold around 200 scopes (mostly between 1979 and 1986), and more TQ than any other make, but contrary to what I thought, NO S52s! A few D52s only, which explains why I though it was unusual. Now I understand why it was more expensive than D52.
Andy, I could go and consult my old valve testing book, but I have certainly tested dozens of ECC88 and ECF 80/804s, but never recall any ECC88s with O/C heaters, though there must have been an odd one. My electronics area is chaotic right now, so can't put my hands on my AVO valve data book, but I recall one of the Eccxx valves has an incorrect entry. I THINK it is the ECC88. Are you working from that? When I made a simple jig a couple or so years ago, I created "testing cards" which I placed over the valve holder, to ensure I made the correct connections. I made a point of consulting the manufacturer's valve data book, thereby eliminating possible Avo Valve data book errors. Well worth checking you have that right. Les. |
24th Jun 2018, 9:51 pm | #22 |
Octode
Join Date: Oct 2007
Location: Exeter, Devon, UK.
Posts: 1,553
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Re: Telequipment D/S52
Telequipment s52 and ECC88.
My less extensive experience than MotorBikeLes with ECC88 is that they are pretty reliable. I have checked the Avo Valve Data Book entries (19th and 20th editions)with the valve base connections given by Mullard/Brimar or Wirelesss World valve data booklet. I tend to do the same as MBLes and work from the manufacturers data. For ECC88 and 6DJ8, the Avo data gives either: 7 4 1 2 3 6 4 1 0 or 6 4 1 2 3 7 4 1 0 selector a2 g c h+h-a1 g c - a1 g c h+h-a2 g c - electrode which are effectively the same: 6 and 7 are the two anodes. Take your pick which you call anode 1 for the Anode selector. Both correctly have the heaters at 6v. Different for the ECC81/82/83 series, as they have a 12.6v heater with centre tap open when above settings are valid, or with heater set to 6v, switches to 741 226 413. Where did you get the testing conditions. Perhaps that is why you got such odd results. Va225, Vg -7, should give 5ma, but you are right down on the bottom of the curving characteristic, where surely small tolerances will make a huge difference. Have you tried testing at say Va 100v, Vg -1.5v, Ia 15ma, gm 12ma/v, which is around the normal operating conditionsand quoted in the Avo data book. You mention the E88CC. That is the special quality version but identical to the ECC88. The results you quote seem well outside the end of life tolerance quoted for that valve. wme_bill |
24th Jun 2018, 10:22 pm | #23 |
Heptode
Join Date: Jan 2009
Location: West Lothian, UK.
Posts: 760
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Re: Telequipment D/S52
Checked my OCR copy of Edition 23 1981 and it gives
641 237 510 for both ECC88 and E88CC Looks very wrong to me as second grid would be connected to the screen grid supply.
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25th Jun 2018, 6:11 am | #24 |
Dekatron
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,637
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Re: Telequipment D/S52
thanks Lawrence, I'll check that today. the schematic shows the SW's but like a lot of switching circuits it's busy and less than clear what is happening.
I'm using a homebrew tester I made myself, which is essentially two variable 0- 350v HT supplies - anode, g2, a variable 0 to -30v bias supply, and a 0 - 30v 5A htr supply. For simple tests I'm just reading a suitable Ia taken fron the mutual characteristics graphs. I take my connections off the datasheet's, so for the ECC88, like a lot of ECC types connections go from pin 1... a, g, k, h, h, a, g, k, scr "Have you tried testing at say Va 100v, Vg -1.5v, Ia 15ma, gm 12ma/v," I did start testing at higher Ia, but exceeded Ia max. i noticed this when a valve red plated. What was happening is that old tired valves tested ok, good ones shot up, then down on the Ia meter. Your example means the valve is exceeding it's Ia max (1.8w) @ 3.3w Bill, which can't be right. If you look at the ECC88 datasheet, there are (unusually for a triode) two mutual characteristics graph's, 0 - 100mA and 0 - 20mA, I used the second. See - http://www.r-type.org/pdfs/ecc88.pdf So using my tester I get a feel for if a valve is a good un after testing a few; good examples quickly reach full current, other's are slow, but with a lot of the ECC88's, I'd insert the valve ( heater power on as is HT, I'm "hot swopping" ) then get nothing after 8 secs or so. Looked at valve, no heater glow, jiggle valve in base, still nothing, valve out, wire brush on pins, still nothing, another jiggle, nada so zap with 12.6v momentarally.... valve htr's lit. Some went on to test ok, Some didn't. So tested continuity with meter, had non OC, but I have several that when inserted won't power up. I can only conclude that the ones with iffy htr's is down to sitting in old dirty scopes for years. A lot of the ones I tested came out of an old Tek 545B which was minging, as was the S52 (I found a moth in the CRT housing). The last cal sticker was 80 something (on the Tek), that's a lot of years sitting in less than ideal storage (and rats/mice had been in redecorating). Lastly when working on this scope and the D43 I was getting lots of wrong readings when testing DC conditions, I got the D43 working by swopping valves blindly, hence the testing. Andy.
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25th Jun 2018, 9:25 am | #25 |
Dekatron
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,637
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Re: Telequipment D/S52
Back on the scope and can't find the TB fault- TB SW off = dot on screen, TB SW on, dot moves to right
doesn't reappear. I have a pulse at the cathode of MR103, see pic, but no ramp on the the sweep OP, see pic. Tried taking voltage readings which is tricky as there are non on the schematic, so I've been cross referenceing over to the D43 schematic to get an idea. But this is tedious work as component ID #'s are different. Any ideas where to look? It doesn't help that I have no idea how the circuit works. V104 is a LTP, but not as we know it Jim. the trigger pulse goes in the anode, not the grid, why? I have 100v at the anode of MR104, and this trace, see pic 3. Surely there should be something more, I'm getting nowt on the anode of the 2nd triode V104/probe test. One interesting observation - there is no voltage drop across R136/7, which means V104 is drawing no current. I checked that R138 is grounded, there is 42v at the cathode end. I have 0.9v from top of R138 (V104 cathodes) to R134 and 13.8v to R139. Andy.
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Curiosity hasn't killed this cat...so far. Last edited by Diabolical Artificer; 25th Jun 2018 at 9:39 am. |
25th Jun 2018, 10:17 am | #26 | |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Telequipment D/S52
Quote:
Lawrence. |
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25th Jun 2018, 2:36 pm | #27 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Telequipment D/S52
Andy, I'll do a couple of switchery fill ins for the time base schematic, one at the 500ms setting and one at the 500us setting if that's any help, will post in a bit.
Lawrence. |
25th Jun 2018, 6:28 pm | #28 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Telequipment D/S52
Hopefuly I've got it correct...'scuse the scrawl.
Lawrence. |
26th Jun 2018, 5:57 am | #29 |
Dekatron
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,637
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Re: Telequipment D/S52
Bless you Lawrence, that gives me something to go on, much appreciated.
Andy.
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26th Jun 2018, 10:17 am | #30 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Telequipment D/S52
No problem, I would forget trigger and see if you can get the time base free running first to get a trace then take it from there.
Lawrence. |
27th Jun 2018, 7:33 am | #31 |
Nonode
Join Date: Nov 2016
Location: Aberaeron, Ceredigion, Wales, UK.
Posts: 2,869
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Re: Telequipment D/S52
Morning Andy
When you offered me this scope and I declined(see previous post) because I wanted a working one, which is on the way, I didn’t think it would put you to so much trouble. You did say “It was more a labour of love” and I can certainly see that, all very informative. Cheers John |
28th Jun 2018, 6:25 am | #32 |
Dekatron
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,637
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Re: Telequipment D/S52
Now I've started it's hard to stop. It'd be easier to fix for most folk here who are more experienced, still I'm learning. Once running these old valve scopes are usually ok.
I'm getting nowhere at present, though I've been reading an old ETI article "repairing oscilloscopes" Dec 89, Jan 90 that is giving me some idea's. As far as I can figure out these TB's work starting with a Miller circuit to get the ramp, which is started by switching the TB SW on causing a cap to charge, this goes into an integrator or mixer as TQ call it. So the circuit starts but won't restart, have to figure this bit out. I found a S51 in the shed that has the same fault, the S51 manual goes into more detail and I'm following the circuit through. I've tried looking online but can't find a good description of how the TB circuit works, I'll get there but its slow work. Andy.
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28th Jun 2018, 9:31 am | #33 |
Nonode
Join Date: Nov 2016
Location: Aberaeron, Ceredigion, Wales, UK.
Posts: 2,869
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Re: Telequipment D/S52
Andy pm sent.
Cheers John |