Reading the service manual afterwards it looks like Z3 is responsible for providing a stable reference voltage, but VT4 (the BC182) is part of the overload protection circuit. The service manual is attached in the video description above ^ The difference between the schematics and my unit are the E30/2 seems to provide 2 amps whereas my E30/1 has a maximum of 1 amp. I re-counted the transistors earlier and I think I counted 1 less than shown on the diagram, so maybe the E30/2 has an extra transistor there, and looking at the schematics again I think those are VT6 and VT7 (2N3055), so assumed mine just has one whereas the /2 model has 2 of them on the back. Makes me think I could probably mod this to provide 2 amps, if the transformer is the same. Also worth pointing out the main transistor (2N3055) is standard NPN, not a FET. en.wikipedia.org/wiki/2N3055
+GadgetUK164 Was thinking the output transistor would be a bipolar transistor and most probably a 2N3055. Seems to be a lot of old linear power supplies of that era used them.
Yeah! I am thinking I could mod this to output 2 amp, it looks like just the transistor and a resistor needs adding. Just not sure if they uprated the transformer or not. I might give it a go and see what happens. I need to look at the analog display later as well to see if that even goes beyond 1 amp, I cannot remember.
+GadgetUK164 I couldn't see why that wouldn't work. I guess if the transformer is able to safely deliver that sort of current and if the drive transistor can drive both the main output transistors then I think it would more than likely work.
Yes, I think that just run in parallel basically. The only issue I can think of is the meter only displays an amp if you use it on current mode, but I guess I could half that with a quick mod so it shows 2 amps over the 1 amp range.
I know it's years later now but in case anybody comes across this, that cracked yellow rectangular capacitor is a safety capacitor (looks like that one is X class, for connection across the mains I think). So really it should be replaced with another safety cap of the proper type, which depends on whether it's across the mains or mains to ground. The right one has to be used as the failure modes are different and tailored for their particular use cases. As someone else pointed out they're made of paper and make huge amounts of smoke when they fail. Dramatic! Really enjoy your videos btw :)
Rifa capacitors are notorious for popping and smoking out when used. They are sealed in some kind of epoxy that cracks over time, letting moisture inside, which theoretically expands and causes the cap to burst. Anytime you see an epoxy sealed Rifa, replace it immediately. They are time bombs...
+FourX2k3 Thanks =D Yeah, I quite like the analog meter stuff! It's annoying it only has one output but I guess I could dig the other one out of storage, although I am thinking it would be a good idea to swap out 2 or 3 of the caps on the other one now as well.
Just want to say thanks, your videos has inspired me to find old faulty games console to repair, so far I've done a Psp 3000, gba sp, and a ps1. 😊 keep uk the good work!
Great video and repair ! Ah, full regulation by all discrete components. VT4 does indeed look like overload protection in the way it is connected between the differential amp and output buffer.
+bwack Thanks =D Yes, I love working on stuff where you can actually replace nearly all the parts with off the shelf bits and its all separate rather than IC =D
Those clear cased RIFA capacitors just seen to crack with age. The same type is used on BBC power supplies and Commodore 8296 etc. but in those they are across the mains and when they go, they fill the room with smoke. These days I replace any of those I find before powering anything on.
+Dave Curran Is the type of replacement I used OK for that one? I am not that hot on the different types of capacitors and where one type should be used over the other (despite same capacitance / voltage etc).
+GadgetUK164 They look fine. Axial is better if you can get them, purely to fit better mechanically. The only ones that need to be careful with are when they are used direct on the mains, and they need to be X2 rated. That looked to be an X rated cap (not in that way), but it didn't need to be as it was just smoothing the output (up to 30V DC). General rule is same or higher with voltage and capacitance unless it is being used for timing circuits etc. Old stuff would usually have been designed expected -20% / + 80% tolerance, so modern 220uF would do for vintage 150uF etc. Modern ones tend to read low, old ones tend to read high unless they are duff. The performance can be very different at different frequencies, and older caps may read OK but be no good in use. I try not to replace things unnecessarily, but electrolytic caps and those film ones are often worth doing. The modern ones won't be as good as the originals were when new, but they are usually better than they are now, if that makes sense.
Thanks! I was mostly concerned about that 630v 100nF - which I replaced with a Polypropylene Axial Metal Film - Not sure what the original (cracked) one was exactly.
+GadgetUK164 The square boxed one is the RIFA one I was talking about. The one that was across the output was just smoothing it a bit. It looks like it's omitted from the later schematic, so they didn't bother with it. That replacement should be fine. They may have overspecced it in case you connected a higher voltage across the output terminals, but you would have more problems if that happened, it should never be more than the 30 ish volt output. Probably that was the best fit they had at the time and it happened to be higher voltage than required.
I have the L30-2 and it's my main bench PSU. The ripple and noise is very good. I need to move to a digital bench PSU for finer adjustments and more functionality
For me I need to be able to dial in low currents when in CC mode into the 5, 10, 20 mA range.. I just can't do that with my L30-2. Also the OV and OC modes, memories are nice along with data logging on the TENMA digital BPSU
I remember these PSU's from college (81-83) That screw in the middle under the meter is a mechanical adjustment to zero the needle ( On a level surface). I don't think the power transistor at the back would be a FET, a bit too old for that, it would more than likely be the humble 2N3055. Caps you changed wouldn't be worth keeping because of their age. Nice video. well executed........
+Michael Hawthorne Yes, you're spot on! It does use the 2N3055, I've just bought some spares. I know caps are generally not worth keeping for their age - I just don't like throwing old working caps. It's a mute point anyway now since I've tested their ESR and all of the caps I replaced had high ESR, so they were binned ultimately. Thanks for watching and commenting =D
Hi great video and good comments. I have the Lt30-1 30v / 1amp. Did you ever mod this to 2amps if so could you possibly show the circuit also the caps you replaced and values would be greatly appreciated,many thanks for the videos.
The schematics were linked somewhere in the video description I think - you can get the cap sizes off there! I didn't mod it, as I suspect it has a different transformer with an extra winding perhaps?
just fixing my l30b, you just cant use them for charging batteries lol, well you can, unless the power goes out, there not protected against current being pushed into them. common failure mode. usually, vt8(bc182) goes short, no not mine, its somewhere else and i cant find it... yet....
Gadg If you can easily access the POT for controlling the voltage can you tell me what the value is? i have a homemade 32V DC PSU and want to be able to vary it. Cheers and thanks in advance(if yo can tell me what value the POT is)
+Amy Marie You cannot just use a pot on its own, you need some other resistors at least to help form a potential divider, ie. to stop high current burning out the pot when you set it too low. And if you feed the output through a pot, the pot needs to be suitable wattage capability to handle any load you pull through it. If you take a look at the schematics in the video description (in the service manual), you can see all the pots on the board and the sizes.
nice restore! :D Good to see something a little Different. don't Reuse those caps. if you want to be sure, you need an ESR Meter.one that tests up to 500Volts.
+Amy Marie I've got an ESR meter but I let a friend borrow it ages ago. I do also have a cheap chinese ESR meter but I guess it's reasonably accurate. I will dig it out later and test the ESR on them. I don't think voltage really matters when it comes to the ESR check - It uses a very high frequency pulse I think in order to calculate the ESR.
@@GadgetUK164 Like Mark I worked at Wetherby (Sept74-Apr 91 and in repair dept 78 onwards). Still doing repairs but now on Medical equipment in a Hospital. Still have an Farnell L30-2T that was assigned to me when I started in 91 and still going strong.
Hi, great and informative hands on video. However, when it comes to really test an old cap properly you need to perform 3 separate kinds of tests to each capacitor to conclude if a cap is good or bad: 1. Capacitance 2. ESR/EPR 3. Leakage test (this is the most important) I came across (no end of times) to old caps showing spot on capacitance value, with relatively low ESR (within the specified ESR limits) but failed miserably when measured for leakage test. So, i'm very picky when it comes to selecting what old caps are good to be reused and what aren't, but I can honestly say as a general rule.....7 times out of 10 they need replacing.
I've got a video coming up where I will test the hundreds of caps I've taken off boards over the last few years, I check them for all 3 things and more then 95% of them are fine in all respects! Caps in certain areas of boards (PSUs particularly) fail a lot, but many of the ones on motherboards are usually fine.
![เปิดบ้าน โคตรสวย ป๋องกพล รู้จักตั้งนาน เพิ่งรู้ว่ารวย!!! l [Nickynachat]](http://i.ytimg.com/vi/tmgCF_2HfYI/mqdefault.jpg)
Reading the service manual afterwards it looks like Z3 is responsible for providing a stable reference voltage, but VT4 (the BC182) is part of the overload protection circuit. The service manual is attached in the video description above ^
The difference between the schematics and my unit are the E30/2 seems to provide 2 amps whereas my E30/1 has a maximum of 1 amp. I re-counted the transistors earlier and I think I counted 1 less than shown on the diagram, so maybe the E30/2 has an extra transistor there, and looking at the schematics again I think those are VT6 and VT7 (2N3055), so assumed mine just has one whereas the /2 model has 2 of them on the back. Makes me think I could probably mod this to provide 2 amps, if the transformer is the same. Also worth pointing out the main transistor (2N3055) is standard NPN, not a FET.
en.wikipedia.org/wiki/2N3055
+GadgetUK164 Was thinking the output transistor would be a bipolar transistor and most probably a 2N3055. Seems to be a lot of old linear power supplies of that era used them.
Yeah! I am thinking I could mod this to output 2 amp, it looks like just the transistor and a resistor needs adding. Just not sure if they uprated the transformer or not. I might give it a go and see what happens. I need to look at the analog display later as well to see if that even goes beyond 1 amp, I cannot remember.
+GadgetUK164 I couldn't see why that wouldn't work. I guess if the transformer is able to safely deliver that sort of current and if the drive transistor can drive both the main output transistors then I think it would more than likely work.
Yes, I think that just run in parallel basically. The only issue I can think of is the meter only displays an amp if you use it on current mode, but I guess I could half that with a quick mod so it shows 2 amps over the 1 amp range.
I know it's years later now but in case anybody comes across this, that cracked yellow rectangular capacitor is a safety capacitor (looks like that one is X class, for connection across the mains I think). So really it should be replaced with another safety cap of the proper type, which depends on whether it's across the mains or mains to ground.
The right one has to be used as the failure modes are different and tailored for their particular use cases.
As someone else pointed out they're made of paper and make huge amounts of smoke when they fail. Dramatic!
Really enjoy your videos btw :)
Rifa capacitors are notorious for popping and smoking out when used. They are sealed in some kind of epoxy that cracks over time, letting moisture inside, which theoretically expands and causes the cap to burst. Anytime you see an epoxy sealed Rifa, replace it immediately. They are time bombs...
Great repair, it's always good to have a bench power supply at hand, love the old analog meter stuff.
+FourX2k3 Thanks =D Yeah, I quite like the analog meter stuff! It's annoying it only has one output but I guess I could dig the other one out of storage, although I am thinking it would be a good idea to swap out 2 or 3 of the caps on the other one now as well.
Looks like the 9 years I spent repairing power supplies and other test equipment. Great job my era of repair!
Thanks =D
Some of this old stuff is a bit crusty but its good quality in general and really stands the test of time!
Just want to say thanks, your videos has inspired me to find old faulty games console to repair, so far I've done a Psp 3000, gba sp, and a ps1. 😊 keep uk the good work!
+skm21 Thanks =D Keep up the good work yourself! Sounds like you are doing a good job having restored the systems you've done so far =D
Another interesting video. Glad that you're back too.
+Nina Evans Thanks =D I do have some more videos on the way, just lots going on etc and some parts taking ages to arrive.
Great video and repair ! Ah, full regulation by all discrete components. VT4 does indeed look like overload protection in the way it is connected between the differential amp and output buffer.
+bwack Thanks =D Yes, I love working on stuff where you can actually replace nearly all the parts with off the shelf bits and its all separate rather than IC =D
The battered paint just adds character ;-)
Brilliant video I have this PSU's bigger brother basically two of your units housed in one case. mine was a radio rally buy some years ago.
+JaysVintageJunk JaysVintageJunk Thanks =D Would love to see that unit at some point in a future video! I love all that old kit.
Update 21/02/2016 - Checked the ESR of the 3 old caps I swapped out and all of them had high ESR, so it was a good idea to swap them out.
Those clear cased RIFA capacitors just seen to crack with age. The same type is used on BBC power supplies and Commodore 8296 etc. but in those they are across the mains and when they go, they fill the room with smoke. These days I replace any of those I find before powering anything on.
+Dave Curran Is the type of replacement I used OK for that one? I am not that hot on the different types of capacitors and where one type should be used over the other (despite same capacitance / voltage etc).
+GadgetUK164 They look fine. Axial is better if you can get them, purely to fit better mechanically. The only ones that need to be careful with are when they are used direct on the mains, and they need to be X2 rated. That looked to be an X rated cap (not in that way), but it didn't need to be as it was just smoothing the output (up to 30V DC). General rule is same or higher with voltage and capacitance unless it is being used for timing circuits etc. Old stuff would usually have been designed expected -20% / + 80% tolerance, so modern 220uF would do for vintage 150uF etc. Modern ones tend to read low, old ones tend to read high unless they are duff. The performance can be very different at different frequencies, and older caps may read OK but be no good in use. I try not to replace things unnecessarily, but electrolytic caps and those film ones are often worth doing. The modern ones won't be as good as the originals were when new, but they are usually better than they are now, if that makes sense.
Thanks! I was mostly concerned about that 630v 100nF - which I replaced with a Polypropylene Axial Metal Film - Not sure what the original (cracked) one was exactly.
+GadgetUK164 The square boxed one is the RIFA one I was talking about. The one that was across the output was just smoothing it a bit. It looks like it's omitted from the later schematic, so they didn't bother with it. That replacement should be fine. They may have overspecced it in case you connected a higher voltage across the output terminals, but you would have more problems if that happened, it should never be more than the 30 ish volt output. Probably that was the best fit they had at the time and it happened to be higher voltage than required.
The cap is wired between ground and earth though - Can't understand why that is?
I have the L30-2 and it's my main bench PSU. The ripple and noise is very good. I need to move to a digital bench PSU for finer adjustments and more functionality
Yeah, still a useful PSU! Well built for sure! I need to get a newer digital bench PSU too at some point!
For me I need to be able to dial in low currents when in CC mode into the 5, 10, 20 mA range.. I just can't do that with my L30-2. Also the OV and OC modes, memories are nice along with data logging on the TENMA digital BPSU
I remember these PSU's from college (81-83)
That screw in the middle under the meter is a mechanical adjustment to zero the needle ( On a level surface).
I don't think the power transistor at the back would be a FET, a bit too old for that, it would more than likely be the humble 2N3055.
Caps you changed wouldn't be worth keeping because of their age.
Nice video. well executed........
+Michael Hawthorne Yes, you're spot on! It does use the 2N3055, I've just bought some spares. I know caps are generally not worth keeping for their age - I just don't like throwing old working caps. It's a mute point anyway now since I've tested their ESR and all of the caps I replaced had high ESR, so they were binned ultimately. Thanks for watching and commenting =D
ive built them at the start of my career with farnell electronics when they produced equipment
its a metallised paper capacitor. they fail like that over time, usually with a stinking smoke show.
+MAGIK Thanks =D Lucky for me I didn't have to experience the stinking smoke =D
Hi great video and good comments. I have the Lt30-1 30v / 1amp. Did you ever mod this to 2amps if so could you possibly show the circuit also the caps you replaced and values would be greatly appreciated,many thanks for the videos.
The schematics were linked somewhere in the video description I think - you can get the cap sizes off there! I didn't mod it, as I suspect it has a different transformer with an extra winding perhaps?
just fixing my l30b, you just cant use them for charging batteries lol, well you can, unless the power goes out, there not protected against current being pushed into them. common failure mode. usually, vt8(bc182) goes short, no not mine, its somewhere else and i cant find it... yet....
Double check that mains fuse value. 5A is way too high. More likely 500mA or even 250mA
Gadg If you can easily access the POT for controlling the voltage can you tell me what the value is? i have a homemade 32V DC PSU and want to be able to vary it. Cheers and thanks in advance(if yo can tell me what value the POT is)
+Amy Marie You cannot just use a pot on its own, you need some other resistors at least to help form a potential divider, ie. to stop high current burning out the pot when you set it too low. And if you feed the output through a pot, the pot needs to be suitable wattage capability to handle any load you pull through it. If you take a look at the schematics in the video description (in the service manual), you can see all the pots on the board and the sizes.
yeah i know i have the parts and i did find out what i need and i did start to build it, i found a 5k Pot and some other things that i needed.
+GadgetUK164 i completed an adjustable Circuit based off something i found on the Net
tinypic.com/r/scgj9t/9
nice restore! :D Good to see something a little Different. don't Reuse those caps. if you want to be sure, you need an ESR Meter.one that tests up to 500Volts.
+Amy Marie I've got an ESR meter but I let a friend borrow it ages ago. I do also have a cheap chinese ESR meter but I guess it's reasonably accurate. I will dig it out later and test the ESR on them. I don't think voltage really matters when it comes to the ESR check - It uses a very high frequency pulse I think in order to calculate the ESR.
Built in wetherby yorkshire heatsink wired by me haha
Really? Wow lol! How cool to find someone that worked on these =D
i have a l30b, dead at the minute, but i wont part with it....
@@GadgetUK164 Like Mark I worked at Wetherby (Sept74-Apr 91 and in repair dept 78 onwards). Still doing repairs but now on Medical equipment in a Hospital. Still have an Farnell L30-2T that was assigned to me when I started in 91 and still going strong.
Hi, great and informative hands on video. However, when it comes to really test an old cap properly you need to perform 3 separate kinds of tests to each capacitor to conclude if a cap is good or bad:
1. Capacitance
2. ESR/EPR
3. Leakage test (this is the most important)
I came across (no end of times) to old caps showing spot on capacitance value, with relatively low ESR (within the specified ESR limits) but failed miserably when measured for leakage test. So, i'm very picky when it comes to selecting what old caps are good to be reused and what aren't, but I can honestly say as a general rule.....7 times out of 10 they need replacing.
I've got a video coming up where I will test the hundreds of caps I've taken off boards over the last few years, I check them for all 3 things and more then 95% of them are fine in all respects! Caps in certain areas of boards (PSUs particularly) fail a lot, but many of the ones on motherboards are usually fine.