K8FC,
I think this is the kit you are looking for. He has offered this kit of caps for years:
?
Attached are the details.
Sam W3OHM
Sam Reaves
ARS W3OHM
Owner / Moderator of: LeCroy Owners Group on Groups.io
Sencore Owners Group on Groups.io Sprint Layout Group on Groups.io?? Pulsonix EDA Group on Groups.io
LPKF Owners Group on Groups.io
Electronics and Mechanical Hardware Design Engineering Manager
Staff Scientist Andritz Rolls Global Research Center (RETIRED)
On Sun, Jul 9, 2023 at 8:09?PM dxradio33 < k8fc@...> wrote: I have two power supplies for the 2445b and they both need new caps.? I know a few years ago there were cap kits that included all the key caps to replace in the supply.? My particular issue is with the AC High voltage section as the trace takes about 10 min to finally appear.? I have done some due diligence on the web looking but to no avail.? This is a great scope and I really want to freshen it up.? Any leads to cap kits ?? Or even a list of critical caps that have been replaced in the past would help.? Thanks in advance.
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I have two power supplies for the 2445b and they both need new caps.? I know a few years ago there were cap kits that included all the key caps to replace in the supply.? My particular issue is with the AC High voltage section as the trace takes about 10 min to finally appear.? I have done some due diligence on the web looking but to no avail.? This is a great scope and I really want to freshen it up.? Any leads to cap kits ?? Or even a list of critical caps that have been replaced in the past would help.? Thanks in advance.
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Re: 2247A occasional horizontal jitter
HI.
Are there any other "odd" symptoms?? (Even seemingly unrelated.)
What sort of waveform were you using?? Something with a slope (sine wave) or sharp transition (square or pulse)??? Does it happen on all channels, or just 1 and 2 ?
It could be the trigger threshold changing (if the test signal has a slope being triggered off) or a problem in the horizontal deflection amp.
What sort of sweep speeds and such are you using?? Is the cooling fan (if fitted) working OK?
At least you have another 'scope to use to debug it, I presume you have the service manual, if so, there is usually good methods documented in those to narrow down problems.
Regards.
Dave G8KBV.
--
Created on and sent from a Unix like PC running and using free and open source software:
|
2247A occasional horizontal jitter
I noticed this a few weeks ago, that after about 10-15 minutes I see an occasional horizontal jitter that lasts just for about half to 1 second, and then does not happen again until about another 30 or 60 seconds, sometimes more, sometimes less (no constant rhythm). I confirmed this issue to be in the scope by also sending the same signal to another scope. There is no vibration or physical movement present that could mechanically affect the scope while in use, so I suspect this might be related to a defective cap, perhaps in the sweep section. Or a bad solder joint somewhere? I had not powered up the scope for a few weeks, so kind of forgot about the issue, but while recently using it again was reminded.
Before tearing into this intermittent issue, wanted to ask if anyone with a 224x (or 2252) scope, or in general, has seen anything similar to this, and any suggestions of where to start.
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Background: I was chasing a sweep issue with generous help from people here when R908 caught fire, taking out CR908 and R909. Found Q908 bad.
So...replaced all the above along with Q9070. U930 seemed to have survived the fire as the output transistor showed the same emitter-collector resistance as a new replacement, so I took a chance on not replacing it. For good measure, I replaced U975, the high voltage module.
Lifted and checked diodes and filter caps in the 8.6, 5.2, 30 and 100 volt supplies. All checked good with a Simpson 260 (that's how old I am).
Turned it on for a smoke check (for real in this particular case).
-/+8.6v came up and adjusted nicely, but...
+4.76v at W968 (5.5 norm)
+93.5v at W954 (100 norm)
+28.2v at W956 (30 norm)
Beam find worked normally, bright and center, so I surmise I'm getting HV okay.
Trace shows as two dim dots with posn control almost full right, focus control seems to work, but intensity control has no effect.
So...
Opened W968, 954 & 956 to unload the 5.2, 30 and 100 volt lines.
¡À8.6 still good.
+5.2v came up to normal.
+100 and +30v still read low with no load.
So there seems to be trouble in the 100/30 volt supply.
I know this is getting tedious, but I would appreciate any helpful suggestions.
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2215A power supply component cross-references.
Thanks tto all the people who have helped with my PS problems. I've done some research and come up with some cross references to some of the arcane part numbers in the Tek parts list.
Q908, 930 is a 2N2907A
CR908 is a 1N4152
Q9070 crosses to an IRF720, and is available
U930 is a TL94CN and is available
CR967,70 are 1N5817s
Q938 is a 2N5087 and is available
Q944 & Q928 can probably be subbed with 2N5551s, but I haven't tried it yet.
CR946,7/CR956-963 are fast switching diodes and the problem is that they were put in a TO-92 case and all the subs I come up with are Schottky diodes in much larger cases. The NTE? 587, 574series have thick steel leads and come in a TO-41 case. Attaching whisker leads to adapt to the thru-hole mounts may be the best option.
If anyone has found subs for Q946 & 947, please let us know. For the moment, I think an AF audio power amp ought work.
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On Sat, Jun 17, 2023 at 09:03 PM, 46davis wrote:
Thanks much. I'll try a 1N914 and see if that works. Guessing at substitutions is just shooting in the dark anyway. Some circuits are very tolerant and others very fussy about component characteristics. I have no idea if the 2N5551 is anywhere near close to the Tek part.
============= As I wrote in an earlier message if 2N5551 is the replacement for Q908 it is the wrong type. You need a PNP and 2N5551 is an NPN. Ozan
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Thanks much. I'll try a 1N914 and see if that works. Guessing at substitutions is just shooting in the dark anyway. Some circuits are very tolerant and others very fussy about component characteristics. I have no idea if the 2N5551 is anywhere near close to the Tek part.
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If the supply frequency is line, 50 hz or 60 hz, then the 1n4000 series is fast enough.? If the diodes are used to rectify the output of a 25 Khz inverter, then the 1n4000 series is way too slow, you need faster diodes.? Others know which ones to use.
Harvey
toggle quoted message
Show quoted text
On 6/17/2023 7:54 PM, Sam Reaves wrote: I might add that the diodes in this supply are probably fast types so 1N4000 series would not do on the switch mode side. If the supply is similar to the 2246/2247 series I remember fixing one where half a dozen diodes (sorry I don't remember the types or part numbers) were
leaky. Apparently?this was a common problem.
Sam
Sam Reaves
ARS W3OHM
Owner / Moderator of:
LeCroy Owners Group on Groups.io
Sencore Owners Group on Groups.io
Sprint Layout Group on Groups.io
Pulsonix EDA Group on Groups.io
LPKF Owners Group on Groups.io
Electronics and Mechanical Hardware Design Engineering Manager
Staff Scientist Andritz Rolls Global Research Center (RETIRED)
On Sat, Jun 17, 2023 at 4:09?PM Dave_G0WBX via groups.io <> <g8kbvdave@...> wrote:
I'd be very cautious working on one of those PSU's, without a fully
isolating AC transformer to power the 'scope while you work on it.
One
false move and short something to "Chassis Ground", and BANG! The
SMPS
input side could be catastrophically damaged.
Also, "usually", the "Main" rail of an embedded multi rail SMPS, (the
one with the voltage reference and direct control of the primary
power
switching stage) needs a minimum load, so that there is enough energy
flowing in the magnetics for the other rails to achieve their output.
I'm not familiar with that exact PSU, but as it seems others have
mentioned that there is a good troubleshooting guide, probably
best to
follow that.
"Bad" SMPS transformers?? Yes, it can happen, but "usually" that
results
in (if anything) a brief burst of activity, then nothing, or at
worst,
the primary side power switch stage fails too, then the utility AC
input
fuse fails.
Take care, as the primary side is usually directly connected to the
incoming AC mains, so you cannot easily "scope" that subsystem,
without
a fully isolating transformer*, that then allows you to ground the
primary -ve side, to make 'scoping and probing easier.
(* Check that any such transformer does indeed have a FULLY
isolated/floating secondary to power the instrument under diagnosis.
Some common "Safety isolating" transformers (Power Tool types) the
secondary is center tapped to utility "Ground".? That can again ruin
your day.
NEVER!!!!? "Float" another 'scope to do such things, that will
only lead
to pain (or worse!)
Stay safe.
Dave G8KBV.
--
Created on and sent from a Unix like PC running and using free and
open source software:
|
I might add that the diodes in this supply are probably fast types so 1N4000 series would not do on the switch mode side. If the supply is similar to the 2246/2247 series I remember fixing one where half a dozen diodes (sorry I don't remember the types or part numbers) were leaky. Apparently?this was a common problem.
Sam
Sam Reaves
ARS W3OHM
Owner / Moderator of: LeCroy Owners Group on Groups.io
Sencore Owners Group on Groups.io Sprint Layout Group on Groups.io?? Pulsonix EDA Group on Groups.io
LPKF Owners Group on Groups.io
Electronics and Mechanical Hardware Design Engineering Manager
Staff Scientist Andritz Rolls Global Research Center (RETIRED)
I'd be very cautious working on one of those PSU's, without a fully
isolating AC transformer to power the 'scope while you work on it. One
false move and short something to "Chassis Ground", and BANG! The SMPS
input side could be catastrophically damaged.
Also, "usually", the "Main" rail of an embedded multi rail SMPS, (the
one with the voltage reference and direct control of the primary power
switching stage) needs a minimum load, so that there is enough energy
flowing in the magnetics for the other rails to achieve their output.
I'm not familiar with that exact PSU, but as it seems others have
mentioned that there is a good troubleshooting guide, probably best to
follow that.
"Bad" SMPS transformers?? Yes, it can happen, but "usually" that results
in (if anything) a brief burst of activity, then nothing, or at worst,
the primary side power switch stage fails too, then the utility AC input
fuse fails.
Take care, as the primary side is usually directly connected to the
incoming AC mains, so you cannot easily "scope" that subsystem, without
a fully isolating transformer*, that then allows you to ground the
primary -ve side, to make 'scoping and probing easier.
(* Check that any such transformer does indeed have a FULLY
isolated/floating secondary to power the instrument under diagnosis.?
Some common "Safety isolating" transformers (Power Tool types) the
secondary is center tapped to utility "Ground".? That can again ruin
your day.
NEVER!!!!? "Float" another 'scope to do such things, that will only lead
to pain (or worse!)
Stay safe.
Dave G8KBV.
--
Created on and sent from a Unix like PC running and using free and open source software:
|
I'd be very cautious working on one of those PSU's, without a fully isolating AC transformer to power the 'scope while you work on it. One false move and short something to "Chassis Ground", and BANG! The SMPS input side could be catastrophically damaged.
Also, "usually", the "Main" rail of an embedded multi rail SMPS, (the one with the voltage reference and direct control of the primary power switching stage) needs a minimum load, so that there is enough energy flowing in the magnetics for the other rails to achieve their output.
I'm not familiar with that exact PSU, but as it seems others have mentioned that there is a good troubleshooting guide, probably best to follow that.
"Bad" SMPS transformers?? Yes, it can happen, but "usually" that results in (if anything) a brief burst of activity, then nothing, or at worst, the primary side power switch stage fails too, then the utility AC input fuse fails.
Take care, as the primary side is usually directly connected to the incoming AC mains, so you cannot easily "scope" that subsystem, without a fully isolating transformer*, that then allows you to ground the primary -ve side, to make 'scoping and probing easier.
(* Check that any such transformer does indeed have a FULLY isolated/floating secondary to power the instrument under diagnosis.? Some common "Safety isolating" transformers (Power Tool types) the secondary is center tapped to utility "Ground".? That can again ruin your day.
NEVER!!!!? "Float" another 'scope to do such things, that will only lead to pain (or worse!)
Stay safe.
Dave G8KBV.
--
Created on and sent from a Unix like PC running and using free and open source software:
|
Q908 is a PNP transistor, what you replaced with (2N5551) seems to be an NPN transistor.
What was shorted to burn R908?
Ozan
toggle quoted message
Show quoted text
On Sat, Jun 17, 2023 at 07:53 AM, 46davis wrote:
I want to thank you all for your suggestions and support. Last night I was checking test point voltages when R908 caught fire. The heat wiped out CR908 and damaged R909. Q909 tested bad but appeared undamaged. I replaced the resistors and subbed a 1N4004 for the diode and since I couldn't find any specs on the transistor, which was marked Motorola 034, I subbed a 2N5551. Now the unit is completely dead. The fuse is good, so I suspect either the subs aren't within tolerance of original parts or the IC is shorted or another problem. I'm afraid the unit is "parts or repair." Long lived the scope. I really liked it.
And thank you Wade VK4WM, that is exactly what my scope was doing. Hope you have better luck than I did.
|
I want to thank you all for your suggestions and support. Last night I was checking test point voltages when R908 caught fire. The heat wiped out CR908 and damaged R909. Q909 tested bad but appeared undamaged. I replaced the resistors and subbed a 1N4004 for the diode and since I couldn't find any specs on the transistor, which was marked Motorola 034, I subbed a 2N5551. Now the unit is completely dead. The fuse is good, so I suspect either the subs aren't within tolerance of original parts or the IC is shorted or another problem. I'm afraid the unit is "parts or repair." Long lived the scope. I really liked it.
And thank you Wade VK4WM, that is exactly what my scope was doing. Hope you have better luck than I did.
|
When they all read low like that, it is usually due to a filter cap that is hanging on by its fingernails. The cap puts out excess ripple, and the control sees the peaks of the ripple, but your meter sees the average... Look at the supply that provides the feedback to the inverter. -Chuck Harris On Fri, 16 Jun 2023 17:46:15 -0700 "46davis via groups.io" <fly46davis@...> wrote: Hi Dave,
I unloaded the +8,6v, +5.2v, -8.6, +100v and +30v lines. The 100v
reads 91v, the 30v reads 27v, and the 5.2v is 4.92, or all about 10%
low. The 8.6s wouldn't regulate properly with a load, but I was never
able to get more than 7.7v under load. There aren't any voltages
published for the multivibrator rail, but I've ordered some 6.2v
Zener diodes and if that doesn't help, I'll look into the switching
transistors, etc. Have you ever heard of bad power transformers in
Tek scopes? Thanks for your help. Rich.
|
If the inverter outputs are all low then I'd be looking at the following, in no particular order:
1) inverter duty cycle if too short
2) inverter control signals if cause too short a cycle
3) overcurrent indications where available, which may shut the inverter down
4) bad capacitors to see if the bulk voltages out of the inverter are too low because of current loading
5) any bulk voltages to the inverter (careful with measurements!)
Read up on the inverter controller theory.
Harvey
toggle quoted message
Show quoted text
On 6/16/2023 8:46 PM, 46davis via groups.io wrote: Hi Dave,
I unloaded the +8,6v, +5.2v, -8.6, +100v and +30v lines. The 100v reads 91v, the 30v reads 27v, and the 5.2v is 4.92, or all about 10% low. The 8.6s wouldn't regulate properly with a load, but I was never able to get more than 7.7v under load. There aren't any voltages published for the multivibrator rail, but I've ordered some 6.2v Zener diodes and if that doesn't help, I'll look into the switching transistors, etc. Have you ever heard of bad power transformers in Tek scopes?
Thanks for your help.
Rich.
|
Hi Dave,
I unloaded the +8,6v, +5.2v, -8.6, +100v and +30v lines. The 100v reads 91v, the 30v reads 27v, and the 5.2v is 4.92, or all about 10% low. The 8.6s wouldn't regulate properly with a load, but I was never able to get more than 7.7v under load. There aren't any voltages published for the multivibrator rail, but I've ordered some 6.2v Zener diodes and if that doesn't help, I'll look into the switching transistors, etc. Have you ever heard of bad power transformers in Tek scopes?
Thanks for your help.
Rich.
|
Thank you for that. It helps.
On Friday, June 16, 2023 at 06:18:40 AM CDT, Mike Dinolfo <mdinolfo@...> wrote:
Also, check in the Tekscopes group
(maybe not available in Tekscopes2) under Files; look for
which is described (quite accurately, I
think) as "Very good document on repairing 22xx Power Supplies
made by H?kan, aka Zenith"
Mike N4MWP
On 6/16/23 05:26, Froggie the Gremlin
wrote:
Hello, fixing the TEK portables is not so difficult, many hams, DIYers, and techs suceeded
suggest you get the service manual for,your serial number, see flowchart on power,supply and CRT,CKTs.
The PSU s of most portable tek are not exotic, 120/240...rect>>360 VDC>>Switcher>>DC busses>>final linear regulators.
Photo of the trace will benefit debugging, but suspect blanking in CRT circuit
Search Both TEKSCOPES2 and Tekscopes on groups.io and also,search eevblog.
Bon chance
Jon
|
Thanks much for that advice. I will try unloading the PS and take the voltages.
The last time I really did much in-depth troubleshooting was in avionics in the old days and there were much more detailed procedures and measurements and test points.
|
Take care troubleshooting PSU's where an output "seems" not to regulate properly / not achieve the specified voltage.
General advice, valid for all sorts of systems, not just 'scopes...
That rail's regulator may be in Current Limit!? That could be due to a fault elsewhere in the 'scope, or the current sense circuit becoming too enthusiastic about going into limit.
Take care...
Dave G8KBV.
--
Created on and sent from a Unix like PC running and using free and open source software:
|
Also, check in the Tekscopes group
(maybe not available in Tekscopes2) under Files; look for
which is described (quite accurately, I
think) as "Very good document on repairing 22xx Power Supplies
made by H?kan, aka Zenith"
Mike N4MWP
On 6/16/23 05:26, Froggie the Gremlin
wrote:
toggle quoted message
Show quoted text
Hello, fixing the TEK portables is not so difficult, many hams, DIYers, and techs suceeded
suggest you get the service manual for,your serial number, see flowchart on power,supply and CRT,CKTs.
The PSU s of most portable tek are not exotic, 120/240...rect>>360 VDC>>Switcher>>DC busses>>final linear regulators.
Photo of the trace will benefit debugging, but suspect blanking in CRT circuit
Search Both TEKSCOPES2 and Tekscopes on groups.io and also,search eevblog.
Bon chance
Jon
|
Sam Reaves
dxradio33
Mike Dinolfo