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Old 25th Dec 2020, 11:02 am   #41
JohnMcGivern
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Default Re: Fluke 3092 200Mhz power problem

Dont know if this will help format microsoft excel spreadsheet.
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Old 28th Dec 2020, 11:07 am   #42
JohnMcGivern
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Default Re: Fluke 3092 200Mhz power problem

Took power supply out of case today. Started again. Tested all 32 pins to gnd only +58v appears shorted I will attempt to trace this line and check components, finding this difficult to follow schematic especially where a node ends and then continues on another page even the pin connections are hard to follow the eevblog was spot on, not for diy. I just don't want to damage anything else these boards look very fragile.
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Old 28th Dec 2020, 4:10 pm   #43
factory
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Default Re: Fluke 3092 200Mhz power problem

Quote:
Originally Posted by JohnMcGivern View Post
Factory, added 2x60w lamp holders now have 180w lamp limiter.
Checked batteries voltage was 3.12v.
What could have caused 10uF 50v cap to short, is the voltage rating enough.
Schottky diodes v1279/80 there are two values to pick from 30mA and 130mA rating service manual doesn't say.
Where is the battery in this scope? I can't see it in any pictures on the web, have you got voltage at the other end of the two Schottky diodes?
Could having the DMM set to ohms when connected to the 10uF capacitor be confused by voltage (if it was there)?

Quote:
Originally Posted by JohnMcGivern View Post
Took power supply out of case today. Started again. Tested all 32 pins to gnd only +58v appears shorted I will attempt to trace this line and check components, finding this difficult to follow schematic especially where a node ends and then continues on another page even the pin connections are hard to follow the eevblog was spot on, not for diy. I just don't want to damage anything else these boards look very fragile.
Yes I would be careful with any soldering on these boards, especially if they have traces on both sides, maybe some boards have internal traces too, plus those glued down SM parts.
Probably worth practising on a scrap board from something worthless first, if you haven't worked on anything like this before.

Re: the +/-58V rails, you've noted a short (100ohms ish) here before around R1291 which I thought was the resistor & transformer winding being measured.
If the output of the +58V appears shorted you should check the diodes & capacitors in the area. If your DMM has a diode mode, use that to check across the diodes both ways (not to ground for the ones not connected to ground).
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David

Last edited by factory; 28th Dec 2020 at 4:19 pm.
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Old 28th Dec 2020, 9:01 pm   #44
JohnMcGivern
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Default Re: Fluke 3092 200Mhz power problem

Hi David, I was just poking around the caps again and I touched the top of vent area on cap basically by accident and it buzzed out on my meter so I tried it on all other visable caps and found another so 2 caps seem to be shorted one on the 5v rail the other on the _5.2 rail I will double check tomorrow. I am sorry for any inconvenience my inexperience has caused I report what I find then next day it's not there anymore it's as though something turns on or off i.e. transistor Thyristor. I think you are right David I measured the same cap and got 102ohms like you said 100E resistor plus transformer winding. Anyway I hope when I replace the 2 caps tomorrow I may get better readings I keep thinking of the guy on the eevblog having a nightmare. I don't have his experience so will take my time. David I will check voltage at the diodes they are v1279/80 battery attached to 2 pin connector beside fan connector.
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Old 30th Dec 2020, 11:48 am   #45
JohnMcGivern
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Default Re: Fluke 3092 200Mhz power problem

Hi David, can you tell me what to expect from R1231 its on page 5.6-11 right beside C1291 102ohm cap I think its a ptc. taking resistance reading it starts around 6oo ohms rise quite fast to 1150 then creeps up to around 1274 ohms I know it says 1.5kohm and is connected to op amp LM339 pin 8 I assume this is the temp sensor I wanted to know if the ohms reading should be stable as it is erratic.
Sorry if I am jumping all over the place but when I recheck things the next day they are different put it down to old age. Many thanks.
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Old 30th Dec 2020, 2:46 pm   #46
factory
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Default Re: Fluke 3092 200Mhz power problem

What was the ambient temperature before you took the measurement? the 1.5K ohms will be a value for a certain temperature (unknown as I can't find a datasheet), the manuals says it's a NTC type (page 5.6-16), if you warm it up the value should decrease.

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Old 30th Dec 2020, 3:30 pm   #47
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Default Re: Fluke 3092 200Mhz power problem

The temp was about 17*C the resistance is rising not falling I put my finger on the small disc while measuring as mentioned previously the resistance rose from 600 to 1270 was still rising but very very slow. I measured the R1011 = 93.1 ohms page 5.6-15 this is the same value NTC. Would this have caused the changing readings? I don't have one of these I will check a few old boards if not send for some maybe getting somewhere.
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Old 30th Dec 2020, 4:35 pm   #48
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Default Re: Fluke 3092 200Mhz power problem

The NTC should reduce with increasing temperature, it needs to much lower than 600ohm to make pin 8 of the comparator (N1236) higher than the 10V reference, we used the heat-shrink gun to warm them to test them at work, a hairdryer should do for checking it, the manual states pin 14 of the comparator will be low at above 80C.
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As the OVP uses another comparator that will work in the same way, increasing voltage will put pin 10 above the 10V reference and trip that one.
If these are SM components measuring any voltages would be tricky, but not impossible, then again if the PSU shuts down before you can measure these it would be difficult to prove if these are causing it.

David
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Old 3rd Jan 2021, 6:21 pm   #49
JohnMcGivern
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Default Re: Fluke 3092 200Mhz power problem

I removed ntc tried measuring resistors around lm339 all unstable starting low and rising.
If I try cobbling some resistors together which supply voltages should I add the load to or would the lamp limiter be sufficient don't want to do more damage.
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Old 6th Jan 2021, 4:16 pm   #50
JohnMcGivern
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Default Re: Fluke 3092 200Mhz power problem

Happy New Year to all.
When I removed NTC one of the legs fell off managed to measure it out of circuit it was good 1.5 Kohm.
I have been looking for a replacement but this value seems quite rare is this resistance critical as there are plenty of 1 Kohm. The big suppliers have them but the handling charges are rediculous, rant over, go safe.
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Old 7th Jan 2021, 12:15 pm   #51
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Default Re: Fluke 3092 200Mhz power problem

Oh dear, maybe worth posting a wanted post to see if anyone has a scrap board or NTC thermistor of the correct type. I find it difficult to need enough parts to make an order from the big suppliers worthwhile too.

David
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Old 8th Jan 2021, 5:29 pm   #52
JohnMcGivern
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Default Re: Fluke 3092 200Mhz power problem

Thanks David, I managed to order some ntc resistors and also all the load resistor values mentioned in section 8. I could do with help regarding where to attach the load resistors for each voltage a quick hand sketch would be fine. The power supply is out of the case but it is still connected to the CRT,s suction cap. Any advice would be appreciated. Also 180w lamp limiter set up with I/T. Thanks.
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Old 9th Jan 2021, 11:15 am   #53
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Default Re: Fluke 3092 200Mhz power problem

When I've built test loads or test circuits I usually find a matching connector for the board, maybe we can identify the connector if you can post some pictures of both halves.
Once you have a connector it should be possible to solder wires to extend the pins out for the resistors.
We also suggested finding out how to disable the HT for the CRT as recommended in the manual.
It would probably be a good idea to double check everything is going to the correct pins before powering up.

David

Edit: some pictures of the connector here, just none showing the view of the pins.
https://www.eevblog.com/forum/repair...-oscilloscope/
It looks like a standard 64 pin (2x 32 pin) DIN connector, I may have the matching half if there is a space where a middle row of pins would be, something like these but with only two rows of contacts;
https://www.erni.com/en/products-and...-2-connectors/

Last edited by factory; 9th Jan 2021 at 11:42 am.
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Old 9th Jan 2021, 7:52 pm   #54
JohnMcGivern
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Default Re: Fluke 3092 200Mhz power problem

Hi David, I have attached some photo's.
I have pins and female molex connectors single/double/treble etc to connect to pins and resistors.
I notice on the resistor requirements sheet section8 it mentions -5.2V this voltage is not on the pin connector sheet row(A) or row (C) molex block.

I contacted the lad from eevblog he said he would have a look at the scope he repaired and help with the loading arrangements after reading his blog I was wary as I said before.
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Old 13th Jan 2021, 10:09 pm   #55
JohnMcGivern
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Default Re: Fluke 3092 200Mhz power problem

Hi guys, David I think this is the pin connector, I am still waiting for the resistors and the thermistors to arrive can anyone try to confirm if this is the correct connector.
Thanks again.
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Old 13th Jan 2021, 11:20 pm   #56
factory
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Default Re: Fluke 3092 200Mhz power problem

I meant to post these at the weekend but forgot, I have either one with pins cut down or one with longer pins, let me know if one of them would help and I can send one for the cost of postage.
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David
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Old 14th Jan 2021, 9:26 am   #57
JohnMcGivern
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Default Re: Fluke 3092 200Mhz power problem

Hi David, just send what you think is most appropriate and let me know how much for postage and part and preferred method of payment.
I am still not sure about connections are +5v row A and row C joined together when they come out of connector then soldered to +5v resistors then to one common ground or separate grounds.
Same applies to all voltages.
John McGivern
41 Snowdon Crescent,
Redcar
TS10 4AQ

Kind regards, John.

Last edited by JohnMcGivern; 14th Jan 2021 at 9:28 am. Reason: Address
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Old 14th Jan 2021, 10:15 am   #58
JohnMcGivern
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Default Re: Fluke 3092 200Mhz power problem

Just a quicky this attachment shows +5v connections on Rows (C) and (A) and a +5v sense. excuse the bad attempt using paint but I think you will understand.
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Old 14th Jan 2021, 12:06 pm   #59
factory
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Default Re: Fluke 3092 200Mhz power problem

Hopefully the Mods will remove your address, you shouldn't post contact details on posts. I've sent you a personal message (PM) about the connectors.

There are quite a few diagrams showing the connections, I'm a little confused as to where the 5.2V supply is, not sure if it's one of the 5VA ones that is maybe labelled wrong. Possibly wise to check with your meter to confirm which are joined together.
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The sense lines are normally used for compensating for volt drop (from the higher current supply) in the traces from the PSU to the rest of the circuits.
You could either connect separate wires at the load resistor end, or connect together at the connector end, just remember to measure the voltage at the point where they are connected.

Still need to work out how to disable the HT section.

David

Edit: If someone has an original manual showing the second picture of the connector diagram (above) that is clearer that would help a lot.

Last edited by factory; 14th Jan 2021 at 12:12 pm.
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Old 17th Jan 2021, 3:08 pm   #60
JohnMcGivern
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Default Re: Fluke 3092 200Mhz power problem

Still awaiting NTC and resistors in the meantime I have beeped out the connector pins see attachment if it makes sense. I have noted that row A pin31 shows continuity with A and C pin18 I don't know if this is right.
A3 sense pin no continuity with any other pins.
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