GW GOS 3310 oscilliscope

Mohntr · 01-20-2020, 04:51 PM

yec oil-con 0.5 uf 1500wvdc capacitor:

Hi, I pulled the cover on my old scope and was checking for swollen caps and I indeed found 1 that is swollen on the end where the single wire comes out. It also appears it has been hot and the plastic label on it has deformed/shrunk.
I googled the cap name and number and don't seem to be able to find a replacement. I have never seen a cap like these and assume it is NOT an electrolite ?
Could anyone offer advice on finding one or should I make it a paper weight? I was hoping to learn how to use it.

Thanks,

Mohntr

**petehall347** · 01-20-2020, 05:12 PM

post a picture of it

Mohntr · 01-20-2020, 05:19 PM

Here is a picture.

**R_J** · 01-20-2020, 10:33 PM

It is highly likely the cap is ok, it is just the heatshrink on the cap has shrunk due to heat from the 3 thermistors next to it. I believe those are oil filled caps. If the scope is working leave those caps alone. they will likely out last the scope.

**Topcat** · 01-20-2020, 11:38 PM

Quote:

Originally Posted by R_J

It is highly likely the cap is ok, it is just the heatshrink on the cap has shrunk due to heat from the 3 thermistors next to it. I believe those are oil filled caps. If the scope is working leave those caps alone. they will likely out last the scope.

I'm inclined to agree.

Mohntr · 01-21-2020, 09:54 AM

Thanks for replying. The scope is not acting right. It only works for the first 30 seconds or so when I turn it on. When reading the 0.25v internal calibration it is smooth then all of a sudden starts acting erratic and the line is fuzzy, I only opened the case to look for something obvious and that one cap had the deformed sleeve and the end not showing in the picture is swollen compared to all the others next to it.
I could snip one leg out of circuit and test with a meter, but I dont have an esr meter.

**stj** · 01-21-2020, 12:15 PM

probably a bad diode in the HV circuits

**redwire** · 01-21-2020, 09:31 PM

Just lift a leg and test the capacitors' value and for leakage. I see oil-filled capacitors in oscilloscope HV section just don't last. Marcon's in Leader oscilloscopes are notorious for failing. Then they take out the HV rectifier and it's a mess.
If the trace is going fuzzy, then the focus voltage is likely sagging so I would suspect a power supply problem. The three MOV's next to it are typically a shunt-regulator for the high voltage but nothing hot enough to heat up a big can and shrink the heatshrink lol

P.S. When working with the HV capacitors, always discharge them first.

**R_J** · 01-21-2020, 09:53 PM

If the cap is swollen at the end that is not shown in the picture, then replace the 3 of them.

Mohntr · 01-22-2020, 06:37 AM

Thanks for the info, I'll get a picture of the end of the cap after work this evening. I appreciate the help.

**redwire** · 01-22-2020, 12:52 PM

The Marcon brand ones have a hard epoxy seal and no rubber bung.
These old axial caps have no safety vent, but I don't think the oil actually makes gas, unlike electrolytics. I'm not sure what the electrolyte actually is.

**stj** · 01-22-2020, 01:03 PM

pcb's ??
like transformer-oil??

**redwire** · 01-22-2020, 01:28 PM

Electrolytics can't go higher than around 450-500VDC, so for big HV caps I guess oil was used.
I haven't taken one apart, but yes oil like motor starting caps. Some Marcon's have a rubber bung, others have epoxy. The bumble bee capacitors were castor oil.

Three of 0.5uF 1500V C101, C102, C103 are the voltage-doubler and I see a fourth smaller one in OP's pic. I'd just change all of them, put in polypropylene parts from digikey or mouser.

Mohntr · 01-23-2020, 12:40 PM

https://www.dropbox.com/preview/Publ...?role=personal

Mohntr · 01-23-2020, 12:56 PM

https://www.dropbox.com/s/joisx5n6z3...22017.jpg?dl=0

another image, sorry for the two posts.

Mohntr · 01-23-2020, 02:19 PM

C102 shows it is shorted to its case. I can not get a reading of any capacitance with my meter on Cap mode. All other caps I get a reading on cap mode.
I have not taken anything out of circuit.
redwire, may i ask where you found the schematic?

Mohntr · 01-23-2020, 02:22 PM

I was on Mousers website looking for the polypropylene caps and did not see them. Are they called something else by chance?
I'm learning electronics on my own, I have never seen these types of caps before so I want to get the right one(s). Thank you.

Mohntr · 01-23-2020, 02:59 PM

Is this a bad choice?

https://www.ebay.com/itm/2pcs-Bishop...ss!63069!US!-1

**redwire** · 01-23-2020, 04:00 PM

Those eBay caps seem expensive and for audiophile use.

I would consider:
Kemet axial 0.47uF 2000VDC 44mm long 33.5mm dia. Best fit. Mouser has them too.
Wima boxed PP 0.47uF 1600VDC 32mm height.
Kemet R76 series 0.47uF 1600VDC but 37mm high.

The boxed film caps would need HV lead wires added and I glue them to the pcb with some silicone. A bit awkward.

Low cost chinese film caps are called "CBB" but New Years so for 2 weeks shops are closed. I saw 474J 2000V 27mm lead spacing https://www.ebay.com/itm/CBB-Metalli...c/302297220783 $8 for 10.

01-20-2020, 04:51 PM	#1
Mohntr New Member Join Date: Jan 2020 City & State: Catawissa Missouri My Country: USA I'm a: Knowledge Seeker Posts: 10	GW GOS 3310 oscilliscope yec oil-con 0.5 uf 1500wvdc capacitor: Hi, I pulled the cover on my old scope and was checking for swollen caps and I indeed found 1 that is swollen on the end where the single wire comes out. It also appears it has been hot and the plastic label on it has deformed/shrunk. I googled the cap name and number and don't seem to be able to find a replacement. I have never seen a cap like these and assume it is NOT an electrolite ? Could anyone offer advice on finding one or should I make it a paper weight? I was hoping to learn how to use it. Thanks, Mohntr

01-20-2020, 05:12 PM	#2
petehall347 Badcaps Veteran Join Date: Jan 2015 City & State: worcester My Country: United Kingdom I'm a: Knowledge Seeker Posts: 2,007	Re: GW GOS 3310 oscilliscope post a picture of it

01-20-2020, 10:33 PM	#4
R_J Badcaps Veteran Join Date: Jun 2012 City & State: ☻ My Country: Canada I'm a: Professional Tech Posts: 5,365	Re: GW GOS 3310 oscilliscope It is highly likely the cap is ok, it is just the heatshrink on the cap has shrunk due to heat from the 3 thermistors next to it. I believe those are oil filled caps. If the scope is working leave those caps alone. they will likely out last the scope. Last edited by R_J; 01-20-2020 at 10:47 PM..

01-21-2020, 09:54 AM	#6
Mohntr New Member Join Date: Jan 2020 City & State: Catawissa Missouri My Country: USA I'm a: Knowledge Seeker Posts: 10	Re: GW GOS 3310 oscilliscope Thanks for replying. The scope is not acting right. It only works for the first 30 seconds or so when I turn it on. When reading the 0.25v internal calibration it is smooth then all of a sudden starts acting erratic and the line is fuzzy, I only opened the case to look for something obvious and that one cap had the deformed sleeve and the end not showing in the picture is swollen compared to all the others next to it. I could snip one leg out of circuit and test with a meter, but I dont have an esr meter.

01-21-2020, 12:15 PM	#7
stj Great Sage 齊天大聖 Join Date: Dec 2009 City & State: Europe My Country: some shithole run by Israeli agents I'm a: Professional Tech Posts: 21,871	Re: GW GOS 3310 oscilliscope probably a bad diode in the HV circuits

01-21-2020, 09:31 PM	#8
redwire Badcaps Veteran Join Date: Dec 2010 City & State: Alberta My Country: Canada Posts: 1,584	Re: GW GOS 3310 oscilliscope Just lift a leg and test the capacitors' value and for leakage. I see oil-filled capacitors in oscilloscope HV section just don't last. Marcon's in Leader oscilloscopes are notorious for failing. Then they take out the HV rectifier and it's a mess. If the trace is going fuzzy, then the focus voltage is likely sagging so I would suspect a power supply problem. The three MOV's next to it are typically a shunt-regulator for the high voltage but nothing hot enough to heat up a big can and shrink the heatshrink lol P.S. When working with the HV capacitors, always discharge them first.

01-21-2020, 09:53 PM	#9
R_J Badcaps Veteran Join Date: Jun 2012 City & State: ☻ My Country: Canada I'm a: Professional Tech Posts: 5,365	Re: GW GOS 3310 oscilliscope If the cap is swollen at the end that is not shown in the picture, then replace the 3 of them.

01-22-2020, 06:37 AM	#10
Mohntr New Member Join Date: Jan 2020 City & State: Catawissa Missouri My Country: USA I'm a: Knowledge Seeker Posts: 10	Re: GW GOS 3310 oscilliscope Thanks for the info, I'll get a picture of the end of the cap after work this evening. I appreciate the help.

01-22-2020, 12:52 PM	#11
redwire Badcaps Veteran Join Date: Dec 2010 City & State: Alberta My Country: Canada Posts: 1,584	Re: GW GOS 3310 oscilliscope The Marcon brand ones have a hard epoxy seal and no rubber bung. These old axial caps have no safety vent, but I don't think the oil actually makes gas, unlike electrolytics. I'm not sure what the electrolyte actually is.

01-22-2020, 01:03 PM	#12
stj Great Sage 齊天大聖 Join Date: Dec 2009 City & State: Europe My Country: some shithole run by Israeli agents I'm a: Professional Tech Posts: 21,871	Re: GW GOS 3310 oscilliscope pcb's ?? like transformer-oil??

01-23-2020, 12:40 PM	#14
Mohntr New Member Join Date: Jan 2020 City & State: Catawissa Missouri My Country: USA I'm a: Knowledge Seeker Posts: 10	Re: GW GOS 3310 oscilliscope https://www.dropbox.com/preview/Publ...?role=personal Last edited by Mohntr; 01-23-2020 at 01:14 PM.. Reason: trying to make image appear i attached

01-23-2020, 02:19 PM	#16
Mohntr New Member Join Date: Jan 2020 City & State: Catawissa Missouri My Country: USA I'm a: Knowledge Seeker Posts: 10	Re: GW GOS 3310 oscilliscope C102 shows it is shorted to its case. I can not get a reading of any capacitance with my meter on Cap mode. All other caps I get a reading on cap mode. I have not taken anything out of circuit. redwire, may i ask where you found the schematic?

01-23-2020, 02:22 PM	#17
Mohntr New Member Join Date: Jan 2020 City & State: Catawissa Missouri My Country: USA I'm a: Knowledge Seeker Posts: 10	Re: GW GOS 3310 oscilliscope I was on Mousers website looking for the polypropylene caps and did not see them. Are they called something else by chance? I'm learning electronics on my own, I have never seen these types of caps before so I want to get the right one(s). Thank you.

01-23-2020, 02:59 PM	#18
Mohntr New Member Join Date: Jan 2020 City & State: Catawissa Missouri My Country: USA I'm a: Knowledge Seeker Posts: 10	Re: GW GOS 3310 oscilliscope Is this a bad choice? https://www.ebay.com/itm/2pcs-Bishop...ss!63069!US!-1

01-23-2020, 04:00 PM	#19
redwire Badcaps Veteran Join Date: Dec 2010 City & State: Alberta My Country: Canada Posts: 1,584	Re: GW GOS 3310 oscilliscope Those eBay caps seem expensive and for audiophile use. I would consider: Kemet axial 0.47uF 2000VDC 44mm long 33.5mm dia. Best fit. Mouser has them too. Wima boxed PP 0.47uF 1600VDC 32mm height. Kemet R76 series 0.47uF 1600VDC but 37mm high. The boxed film caps would need HV lead wires added and I glue them to the pcb with some silicone. A bit awkward. Low cost chinese film caps are called "CBB" but New Years so for 2 weeks shops are closed. I saw 474J 2000V 27mm lead spacing https://www.ebay.com/itm/CBB-Metalli...c/302297220783 $8 for 10.

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