I guess the lesson is: for fuses on low voltage parts of the board, always remove and test fuse out of the holder. Low voltage suggests low impedance load, and therefore it can easily make your meter beep even if fuse is open. Thanks for showing all of this. Very informative.
I have run into that myself. I saved that fuse because I was putting on electronic traing at a company I worked for. I sure give those guys a go with that fuse. I would chatch them 9 out of 10 times. So much fun with it.
Hugely entertaining as ever Stuart. It's great that you don't edit much content out so it feels like we're there looking over your shoulder as you talk us through each repair job. No trying to spook you though 😂
Hi Stuart, thanks for the video. Sometimes fuse and fuse sockets develop some oxidation, so should clean those before changing. By the way, the push in connectors could also develop some oxidation. I have seen that a lot. Again, good cleaning is often the cure. Have a nice day and thanks again for the video.
This amp is very electrically similar to the Fender Blues Deluxe. Both often have heat-related problems from the position of the valves. I don't know if this could have been the case. However, it is perfectly noticeable when a good technician has experience repairing amplifiers. It was another great video. Cheers
Only someone who never worked on either, nor could read a schematic, would ever compare a Blues Deluxe to a Junior. Since you think a similar name implies an 'electrically similar' amp, I can see where your mistake comes from. You seem to not understand that nearly all combo amps uses the same socket to PCB design as Fender. Heat is NOT a problem in those amps, people who 'mod them' are. Notice the utter lack of heat damage on that board?
A lesson for us all to learn, Stuart. It nevertheless was still an intriguing episode. It had occurred to me that I haven't seen you perform a service on a Hiwatt amp, unless I missed a past episode. Please stay safe. This ever-mutating scourge is another reason to be vigilant in the UK. Cheers!
Having been fooled by the exact same thing on more than one occasion, to test fuses and switches I always try test for voltage across them with the circuit live. If a fuse is good or a switch is closed there is no voltage across it. If the fuse is blown or the switch is open you have full circuit voltage across it. This gets around the issue of testing continuity in a circuit where you may get continuity (or at least low resistance) from other components in the circuit. Anyway, I love your videos and have learned a lot from watching. Keep up the good work!
@@stuartukguitarampguy5830 It's not always possible to do, sometimes you can't get to them, or there may be other problems in the circuit. But if you can it's an easy check. Of course make sure you have a good high impedance meter. if the fuse is blown you don't want the meter to pull so much current it becomes the fuse! Not that I've ever done that! No sir, not me. :)
At 25:40, Stuart says, " There are two different kinds of jacks, god knows why"; Well, I am no deity, and neither is Stuart, but I know "why", and if Stuart thinks about it for a minute he would know why as well: the main output jack is designed to short to ground if there's no speaker-cable plug inserted into it, in order to protect the output transformer from damage caused by operating it without a load. This is and has pretty much always been standard for Fender amplifiers since the 1960s. I'm not sure if the extension speaker jack is wired so that an extension cabinet would work in parallel with the speaker in the amplifier's combo cabinet ---- note that lowering the overall impedance could cause problems for the output tranny ---- or in series so that the impedance increases rather than decreases, or if plugging in an extention cabinet shuts off the combo speaker and the audio only runs through the extension cabinet; but almost certainly there will be some type of built-in switching to minimize the chance of output transformer damage. Note that the Main jack makes metallic contact to the amp chassis,, but the Ext jack is insulated plastic and isolated from the chassis.. PS, the audio signal from the output transformer secondary *needs a chassis ground reference*, otherwise you can't use negative feedback from the output to lower distortion elsewhere in the preamp or phase invertor.
Referencing the spark at 3:40, for discharging caps I use an old Heathkit resistor-substitution box with a rotary selector switch; I can begin at 1K ohms or higher and rotate down to 4 ohms in incremental steps. The original resistors were all 1 watt size, but I increased the lowest ohms-value resistors to 2 W, or 5 W if I had them and they would physically fit.
My background is in electronics (not valves, they were before my time). About 15 years ago I was in a 'The Who' tribute band and became the go-to person to fix the band's equipment. Then it was "My mate's valve amplifier has broken - can you take a look?" It built up from there!
Hate is a strong word, but I hate those glass fuses. Especially the ones sitting in that kind of holder. Have had numerous of them fooled me over the years :)
Considering the amount of force it requires to pull the spade connectors off of those spade lugs mounted on the board, it's generally a good idea to automatically resolder them, simply because as we all know leadfree solder doesn't bond well to larger metal parts such as board-mounted fuse holder clips and spade lug terminals. I suspect that the metallic mass of those larger parts is sufficient that they conduct the heat away a little too quickly as the circuit boards are passed over the wave-soldering machines, and therefore the parts never quite get up to a sufficient temperature for the solder to bond to them. The same thing applies to the potentiometers and especially the input jacks. While you have the board up it's best to just reflow those connections.
Hello Stuart When calculating dissipation of the output tubes on a cathode biased amp which is the correct plate voltage reading to use? i.e. I’ve seen techs measuring from plate to ground and plate to cathode Thanks
Unrelated question: what brand is your magnifying visor? I need a new one and I can't find anything that suits me, but it looks like the one you have is just what I"m looking for. Not that my eyes are getting old or anything... it's just poor lighting... yeah, that's it... poor lighting.... Oddly, I've encountered many intermittent fuses. I usually take them out and give them a little twist and tug just to be sure. It's rare, but it happens. Only takes a second to check.
I’ve got the same issue with my blues jr but all the tubes go on except one of the power tubes, I replaced the tubes but same issue, going to try the fuse next, if that doesn’t work I’ll try checking the tube socket like you did.
Hi Wayne. Great question. An inductor is just a single coil of wire in SERIES with the circuit, so it passes DC just like a wire would. A transformer has two isolated windings, one wound on top of the other. No DC can pass across this. Only AC.
Hi Ian. Ah, I didn;t realise there was a cross Atlantic difference. A 'dry' joint I guess came from being without solder. So the less solder on the joint the drier it is. Basically 'unsoldered' to you and me.
Your touching valves!!! I new a twitchy guy who wore lint free cotton gloves, like a snooker ref, to handle valves. He stated the oil in your fingers would cause the valve to explode. He wore them to handle L.P's as well His wife ran of with a plasterer working on their house
Stuart drives the wrong way up a diagnostic blind alley, so that the rest of us won't have to! [Edit: Now that I'm thinking about it, you British already drive the wrong way anway, so perhaps its just your natural default position for everything else! 🤣]
So you had to take out the whole board to change a fuse that has no real purpose......and it's prob under rated as there would be a surge even using the stand by.......SHM
An ADJUSTABLE WRENCH, held VERTICAL, to remove the input nut? ARE YOU KIDDING ME? This is just proves that a little knowledge can be FAR more dangerous than none. I wouldn't let you sweep the floor of my shop, as you're unqualified to even HOLD A WRENCH, let alone select the proper tool, to not mark up a CHROME control panel. The rest of your 'work' would require a novel to point out and correct.
Hi Kenneth. Sigh, you know after 50 years of doing this sort of thing, I kind of know how to use that wrench without scratching the panel. Astonishing as it may seem. As for the rest, doubtless you are keen to give me the benefit of your superior wisdom and knowkedge, so go for it.
@@stuartukguitarampguy5830 Gee, I guess sockets have no use on earth, and all open wrenches should be used vertical, perpendicular to the handle! This is 50 years of experience claiming, "I'm so good, that my reckless and improper use of tools, is proper! All because I've been objectively wrong for 50 years! I'm an expert in wrong! Only those with experience know the virtues of not using the right tool, and letting juvenile laziness feign 'experience"." Never mind marring up the nut, we need to objectively scratch chrome as well, that everyone saw. Great advice! You're right, everyone should OBVIOUSLY disregard all respect for their customers, because they've been wrong for 50 years, and careless. Hat's off on being an adult, and accepting your error. I'll remember that the next time I make a mistake, I'll tell someone I've been an EE with a multiple degrees for 37 years, so that makes me right. Enjoy the scratches, suckers! Wow, thanks for the lesson! I've seen the light! Well taught!
![[TH] Esports World Cup : Knockout Stage Day 1](http://i.ytimg.com/vi/ES-vr-FarFg/mqdefault.jpg)
I guess the lesson is: for fuses on low voltage parts of the board, always remove and test fuse out of the holder. Low voltage suggests low impedance load, and therefore it can easily make your meter beep even if fuse is open. Thanks for showing all of this. Very informative.
Hi Jim, Yes you've summed it up nicely. I was double fooled by the perfectly intact wire in fuse!
Thanks for being honest and teaching a valuable lesson on fuses!
Cheers Tim.
As always... very informative Stuart! Thank you.
Thanks Rob.
I have run into that myself. I saved that fuse because I was putting on electronic traing at a company I worked for. I sure give those guys a go with that fuse. I would chatch them 9 out of 10 times. So much fun with it.
You Sadist!
Hugely entertaining as ever Stuart. It's great that you don't edit much content out so it feels like we're there looking over your shoulder as you talk us through each repair job. No trying to spook you though 😂
I did feel a strange presence in the workshop when filming....
Great video Stuart, shows your process of fault finding and what can be missed. So informative. Thanks for sharing..Ed..uk..😀
Thanks Ed!
Hi Stuart, thanks for the video. Sometimes fuse and fuse sockets develop some oxidation, so should clean those before changing. By the way, the push in connectors could also develop some oxidation. I have seen that a lot. Again, good cleaning is often the cure. Have a nice day and thanks again for the video.
Thanks Jean-Pierre!
This amp is very electrically similar to the Fender Blues Deluxe. Both often have heat-related problems from the position of the valves. I don't know if this could have been the case. However, it is perfectly noticeable when a good technician has experience repairing amplifiers.
It was another great video.
Cheers
Interesting info, thanks Suso,
Only someone who never worked on either, nor could read a schematic, would ever compare a Blues Deluxe to a Junior. Since you think a similar name implies an 'electrically similar' amp, I can see where your mistake comes from. You seem to not understand that nearly all combo amps uses the same socket to PCB design as Fender. Heat is NOT a problem in those amps, people who 'mod them' are.
Notice the utter lack of heat damage on that board?
Great job! And you fixed two separate problems.
Cheers Zack!
A lesson for us all to learn, Stuart. It nevertheless was still an intriguing episode. It had occurred to me that I haven't seen you perform a service on a Hiwatt amp, unless I missed a past episode. Please stay safe. This ever-mutating scourge is another reason to be vigilant in the UK. Cheers!
Hi Alex
Yes I hardly EVER get a HiWatt amp. I've had maybe 2 in all the time I've been doing this. Not sure why.
@@stuartukguitarampguy5830 Perhaps the design, and high quality components. I rarely see them requiring a service on any channels.
That is why I like your videos.
Great video looking forward to more.
Thanks Jerry!
thanks man had the same problem you turned it into a quick fix
Great that's why I do the vids.
I repaired a few of this ... and you have confirmed that it is a nightmare to remove the main board.
Having been fooled by the exact same thing on more than one occasion, to test fuses and switches I always try test for voltage across them with the circuit live. If a fuse is good or a switch is closed there is no voltage across it. If the fuse is blown or the switch is open you have full circuit voltage across it. This gets around the issue of testing continuity in a circuit where you may get continuity (or at least low resistance) from other components in the circuit.
Anyway, I love your videos and have learned a lot from watching. Keep up the good work!
Hi Richard, that's a really good idea and I've never thought about doung that! Thanks for the useful tip.
@@stuartukguitarampguy5830 It's not always possible to do, sometimes you can't get to them, or there may be other problems in the circuit. But if you can it's an easy check. Of course make sure you have a good high impedance meter. if the fuse is blown you don't want the meter to pull so much current it becomes the fuse! Not that I've ever done that! No sir, not me. :)
@@richardk7256 Me neither! What sort of complete IDIOT would do a thing like that....
worth watching just to see you wrastle that board out. :p Another one lives to play again.
Yes I've done a fair few of those!
Great job!
Thanks Brandon.
Hats off to you Young Stuart!! HATE those damn Circus boards! (Do they shrink them in, in the Factory!!?)
At 25:40, Stuart says, " There are two different kinds of jacks, god knows why"; Well, I am no deity, and neither is Stuart, but I know "why", and if Stuart thinks about it for a minute he would know why as well: the main output jack is designed to short to ground if there's no speaker-cable plug inserted into it, in order to protect the output transformer from damage caused by operating it without a load. This is and has pretty much always been standard for Fender amplifiers since the 1960s. I'm not sure if the extension speaker jack is wired so that an extension cabinet would work in parallel with the speaker in the amplifier's combo cabinet ---- note that lowering the overall impedance could cause problems for the output tranny ---- or in series so that the impedance increases rather than decreases, or if plugging in an extention cabinet shuts off the combo speaker and the audio only runs through the extension cabinet; but almost certainly there will be some type of built-in switching to minimize the chance of output transformer damage. Note that the Main jack makes metallic contact to the amp chassis,, but the Ext jack is insulated plastic and isolated from the chassis.. PS, the audio signal from the output transformer secondary *needs a chassis ground reference*, otherwise you can't use negative feedback from the output to lower distortion elsewhere in the preamp or phase invertor.
The extra socket isn’t for an extension speaker, it’s for a foot switch for the mid boost.
@@ali2ndmail yup, the fat switch remote
Referencing the spark at 3:40, for discharging caps I use an old Heathkit resistor-substitution box with a rotary selector switch; I can begin at 1K ohms or higher and rotate down to 4 ohms in incremental steps. The original resistors were all 1 watt size, but I increased the lowest ohms-value resistors to 2 W, or 5 W if I had them and they would physically fit.
It's my fault, the internal resistor is just to low at 100 ohms. If I change it for a 1K it will be fine.
Brilliant mate.. how did you get started?
Really honest insightful videos. 👍
My background is in electronics (not valves, they were before my time). About 15 years ago I was in a 'The Who' tribute band and became the go-to person to fix the band's equipment. Then it was "My mate's valve amplifier has broken - can you take a look?" It built up from there!
Hate is a strong word, but I hate those glass fuses. Especially the ones sitting in that kind of holder. Have had numerous of them fooled me over the years :)
Considering the amount of force it requires to pull the spade connectors off of those spade lugs mounted on the board, it's generally a good idea to automatically resolder them, simply because as we all know leadfree solder doesn't bond well to larger metal parts such as board-mounted fuse holder clips and spade lug terminals. I suspect that the metallic mass of those larger parts is sufficient that they conduct the heat away a little too quickly as the circuit boards are passed over the wave-soldering machines, and therefore the parts never quite get up to a sufficient temperature for the solder to bond to them. The same thing applies to the potentiometers and especially the input jacks. While you have the board up it's best to just reflow those connections.
Dont use the force, use deoxit
Hello Stuart
When calculating dissipation of the output tubes on a cathode biased amp which is the correct plate voltage reading to use? i.e. I’ve seen techs measuring from plate to ground and plate to cathode
Thanks
Hi Geoff It's plate to cathode. But the cathode resistor only usually drop 10V or so, so it's not THAT much different.
Unrelated question: what brand is your magnifying visor? I need a new one and I can't find anything that suits me, but it looks like the one you have is just what I"m looking for.
Not that my eyes are getting old or anything... it's just poor lighting... yeah, that's it... poor lighting....
Oddly, I've encountered many intermittent fuses. I usually take them out and give them a little twist and tug just to be sure. It's rare, but it happens. Only takes a second to check.
Hi There is no brand name it just says LED HEAD LOUPE on the and. I think I got it from eBay some years ago,
I’ve got the same issue with my blues jr but all the tubes go on except one of the power tubes, I replaced the tubes but same issue, going to try the fuse next, if that doesn’t work I’ll try checking the tube socket like you did.
Ok good luck. Let me know how you get on.
@@stuartukguitarampguy5830 I resouldered the tube socket pin connections like you did and that worked. Thanks to your video!
@@stratmancruthers Wow, awesome, Well done.
Hi Stuart. Do you need the service manual to this amp?
Thanks Monty I have it.
My Blues Junior has worn out grommets in the aluminium U-profile. Where can I buy new one? Is that rubber or silicone grommets?
Hi Rob I wasn;t quite sure which grommets you menat?
STUART UK, how does the output transformer block high voltage DC 350vdc to 600vdc because inductors PASS DC?
Hi Wayne. Great question. An inductor is just a single coil of wire in SERIES with the circuit, so it passes DC just like a wire would. A transformer has two isolated windings, one wound on top of the other. No DC can pass across this. Only AC.
What is a "dry joint"? Is it the same as what we call a "cold solder joint" here in the States?
Hi Ian. Ah, I didn;t realise there was a cross Atlantic difference. A 'dry' joint I guess came from being without solder. So the less solder on the joint the drier it is. Basically 'unsoldered' to you and me.
@@stuartukguitarampguy5830 Oh, OK. That would be what I've always heard referred to as a "solder starved joint".
@@ianaintsaying1625 So what's a cold joint then?
Exactly that. A joint that didn't get good heat transfer which doesn't allow the solder to fully melt and flow.
Your touching valves!!!
I new a twitchy guy who wore lint free cotton gloves, like a snooker ref, to handle valves.
He stated the oil in your fingers would cause the valve to explode. He wore them to handle L.P's as well
His wife ran of with a plasterer working on their house
Probabyl wore them to handle his wife too!
@@stuartukguitarampguy5830 Ha Ha👍
HAAAAA !!!!😆
Stuart drives the wrong way up a diagnostic blind alley, so that the rest of us won't have to! [Edit: Now that I'm thinking about it, you British already drive the wrong way anway, so perhaps its just your natural default position for everything else! 🤣]
Ha ha! Can;t believe I fell for that old problem of measuring the fuse whilst still in the holder!
So you had to take out the whole board to change a fuse that has no real purpose......and it's prob under rated as there would be a surge even using the stand by.......SHM
Yep!
An ADJUSTABLE WRENCH, held VERTICAL, to remove the input nut? ARE YOU KIDDING ME?
This is just proves that a little knowledge can be FAR more dangerous than none. I wouldn't let you sweep the floor of my shop, as you're unqualified to even HOLD A WRENCH, let alone select the proper tool, to not mark up a CHROME control panel. The rest of your 'work' would require a novel to point out and correct.
Hi Kenneth. Sigh, you know after 50 years of doing this sort of thing, I kind of know how to use that wrench without scratching the panel. Astonishing as it may seem. As for the rest, doubtless you are keen to give me the benefit of your superior wisdom and knowkedge, so go for it.
@@stuartukguitarampguy5830 Gee, I guess sockets have no use on earth, and all open wrenches should be used vertical, perpendicular to the handle! This is 50 years of experience claiming,
"I'm so good, that my reckless and improper use of tools, is proper! All because I've been objectively wrong for 50 years! I'm an expert in wrong! Only those with experience know the virtues of not using the right tool, and letting juvenile laziness feign 'experience"."
Never mind marring up the nut, we need to objectively scratch chrome as well, that everyone saw. Great advice!
You're right, everyone should OBVIOUSLY disregard all respect for their customers, because they've been wrong for 50 years, and careless.
Hat's off on being an adult, and accepting your error. I'll remember that the next time I make a mistake, I'll tell someone I've been an EE with a multiple degrees for 37 years, so that makes me right. Enjoy the scratches, suckers!
Wow, thanks for the lesson! I've seen the light! Well taught!
@@kennethc2466 I expect you are right.