Another uncommon amp for us today! You put a spider web in that thing while testing it; You are braver than I. I'm glad to hear you sleep on things. I do the same and it seems to help. I always enjoy your explanations also I learn every time. Thanks again for some entertaining education.
Stu, Uncle Doug has some very good videos that break down Class A and push-pull circuits that are very informative for those that want to learn. I've learned over the years that putting fresh eyes on a problem can often help in troubleshooting. Good job sleeping on it mate.
If the filter cap was on its way out why leave it in circuit (and put another cap in parallel)? I must be missing something. And why not replace the shorted cap as well? I'm confused.
@stevepi1 it certainly can but that is not how Stuart chose to do it. It can also be laid parallel as it was. Splitting hairs. The best way to do it is to remove the board and replace the cap. If you are not doing that then laying parallel or cutting out is the next option. Both as rough as each other but serviceable.
@@rgbplumbinghilton The "next" option is to remove and replace from the top ( j hook or similar) You can leave untested and suspect components in circuit if you wish but it's the least desirable option.
Oh Stuart, don't belittle yourself, you've frequently displayed many fault finding scenarios, the success of which, relied solely on your years of EXPERIENCE. I've taught countless degree level students who can regurgitate all the theory but would stand little chance of fault finding to component level as quickly as you. There's no substitute for many years of "hands on" and enthusiasm for the subject. You have both in abundance. Best regards.
Why would a dropping resistor reduce the 60hz Hum? the dropping resistor just steps down drops down the B+ voltage. What does the B+ stand for? B+ meaning what
Hi Wayne Think AC not DC. The dropping resistor and the large value HT cap to ground form a low frequency rejection circuit. Imagine say a 10k in series with a 100ohm. Other end of 100ohm is at ground, inject 50Hz into top end of 10k. You’d measure a WAY smaller 50hz signal at the junction of the two resistors, wouldn’t you? The ‘100 ohm’ resistor is actually the AC impedance of the 22uF cap. Hope that helps. Back in the day they just arbitrarily labelled the various DC voltages as ‘A’, ‘B’, ‘C’ Etc and they have hung over. So B+ is just one of the hT voltages
What's the value of the second dropping resistor directly above the non-functioning 22mf cap? By your schematic it should be 22k but that doesn't look red/red/orange to me, and that resistor has also obviously been fiddled with...
It looks like 22K to me; it's not unusual to see red stripes on a metal film resistor that are sort of brownish to the eye, especially if the resistor runs warm/hot, and especially when you photograph them; but I didn't see any other metal film resistors like it in the amp, and my guess would be that it's not original (it's elevated up off the board and smears of rosin flux are visible).
That 22k metalfilm resistor is obviously non-original. I would have been asking myself, why did to 10K resistor burn open? It feeds the 6L6 screen, and therefore a shorted output tibe may have been at fault. Was that 6L6 original, or a replacement? If original, it wont be trustworthy ( could have an intermittent short). I would also have checked the mains fuse, and HT fuse if it has one, because the incompetent previous servicer might have used incorrect fuse values. Finally, a shorted output tube, if thats what occured, can damage the heater supply balancing (centertap) resistors; they should have been checked for value and tolarance with an ohmmeter. Always best to ask "why?" rather than just replacung the obviouly damaged components.
HI There's a but more to this one than meets the eye apparently. See the comment from the guy who said Fender might have done that cut-track mod. No HT fuse with this one. If so, I'm wondering if that smaller 22uF radial cap is actually still in circuit somehow and that's why adding another in parallel had no effect. Seems a bit of a mess from Fender tbh. I did a lot o asking 'why' I felt. I may have come to the wrong concluion but I certainly had a theory about what had gone on.
A tech pro guy (Rat Valve Amp) talking about the buzz and Hum of this amp: Another 'Issue' with the Stock Amp is the HIDEOUS Level of Background Noise (Severe Buzz and Hum). There are three main problems: (1) The Output Transformer (OPT) is too close to the Mains Transformer and Causes a Pronounced 'HUM' when the Amp is first switched on, even before it warms up - Simple Fix, Move the OPT away from the Mains Transformer - Done. (2) Not enough Smoothing in the Power Supply which causes the Amp to 'BUZZ' - I have Corrected that. (3) A Design Error on the Main PCB has caused an 'Earth Loop' in the Circuit, which is responsible for most of the Buzz and Hum in the Amp. Unbelievable in a Fender Amp and totally unacceptable. Fender know there is a problem because they have made a 'Half-Ass' effort to correct it by cutting PCB Tracks here and there and adding lengths of wire to the Board, with no success. It took awhile to Find the Error, but I found it and corrected it. The Result - The Amp is now 'SILENT' - NO Background Noise, it's so Quiet that it is difficult to tell if the Amp is On or Off."
So are you saying that cut track and black wire were Fender mods? I'd love to know what the error was that you found. The amp hum was just about acceptable but I'd like to get it lower if possible.
Interesting. Too late now, but try fender ramparte schematic on tdpri. A real schematic, allegedly, and also a forum (War and Peace) on fixing hum. The schematic (which may be rubbish of course) shows 1k for the resistor and only 416V on the first cap.
@@stuartukguitarampguy5830 Any comment with anything resembling a site gets pulled by YT (so infuriating and time wasting). Try the normal ending to tdpri. Then search, fender ramparte schematic, then the Blackstar post. I also sent stuff to your YT addr.
I don't comment very often but I always enjoy your vids and thank you for all your work! Keep them coming. Cheers from usa.
Thanks very much.
Thanks Stu, Very informative video. The ups & downs that can go on in a repair.
Amazing tenacity. Thanks Stewart.
The Fender Ramparte amp was part of Fender's Pawn Shop series of amps.
Thanks Ernest.
Another uncommon amp for us today! You put a spider web in that thing while testing it; You are braver than I. I'm glad to hear you sleep on things. I do the same and it seems to help. I always enjoy your explanations also I learn every time. Thanks again for some entertaining education.
Cheers Michael.
Hi Stuart. It's great to see another in-depth amplifier adventure!
More songs please Stuart !
Stu, Uncle Doug has some very good videos that break down Class A and push-pull circuits that are very informative for those that want to learn. I've learned over the years that putting fresh eyes on a problem can often help in troubleshooting. Good job sleeping on it mate.
Yes it's strange how that works!
Thank you for your fun and educational videos Stuart! I really love watching you repair and explain.
I really enjoyed that video from you, as always. Many thanks for it.
Thanks MArtin
Thanks Stuart for another very interesting and honest video.
Thanks David
Great ending to the video Stuart.. That was a bit of a tricky one to say the least.
Yes got there in the end!
If the filter cap was on its way out why leave it in circuit (and put another cap in parallel)? I must be missing something. And why not replace the shorted cap as well? I'm confused.
Stuart states, its not worth taking the board out on this amp as it is a pain to get out and back in, making the repair cost more than the amps worth.
Yes see comment below. Also, maybe this 47uF was actually ok (I'm thinking it was now) and all I've done is increase its value.
@@rgbplumbinghilton It can be cut out from the top without removing the board.
@stevepi1 it certainly can but that is not how Stuart chose to do it. It can also be laid parallel as it was. Splitting hairs.
The best way to do it is to remove the board and replace the cap.
If you are not doing that then laying parallel or cutting out is the next option. Both as rough as each other but serviceable.
@@rgbplumbinghilton The "next" option is to remove and replace from the top ( j hook or similar)
You can leave untested and suspect components in circuit if you wish but it's the least desirable option.
Many thanks Stuart.
Oh Stuart, don't belittle yourself, you've frequently displayed many fault finding scenarios, the success of which, relied solely on your years of EXPERIENCE. I've taught countless degree level students who can regurgitate all the theory but would stand little chance of fault finding to component level as quickly as you. There's no substitute for many years of "hands on" and enthusiasm for the subject. You have both in abundance. Best regards.
Why would a dropping resistor reduce the 60hz Hum? the dropping resistor just steps down drops down the B+ voltage. What does the B+ stand for? B+ meaning what
Hi Wayne
Think AC not DC.
The dropping resistor and the large value HT cap to ground form a low frequency rejection circuit.
Imagine say a 10k in series with a 100ohm. Other end of 100ohm is at ground, inject 50Hz into top end of 10k.
You’d measure a WAY smaller 50hz signal at the junction of the two resistors, wouldn’t you?
The ‘100 ohm’ resistor is actually the AC impedance of the 22uF cap.
Hope that helps.
Back in the day they just arbitrarily labelled the various DC voltages as ‘A’, ‘B’, ‘C’
Etc and they have hung over. So B+ is just one of the hT voltages
What's the value of the second dropping resistor directly above the non-functioning 22mf cap? By your schematic it should be 22k but that doesn't look red/red/orange to me, and that resistor has also obviously been fiddled with...
It looks like 22K to me; it's not unusual to see red stripes on a metal film resistor that are sort of brownish to the eye, especially if the resistor runs warm/hot, and especially when you photograph them; but I didn't see any other metal film resistors like it in the amp, and my guess would be that it's not original (it's elevated up off the board and smears of rosin flux are visible).
Yes pretty sure that was 22k.
Always a fan here in OregonUSA
Thanks Darrel
That 22k metalfilm resistor is obviously non-original. I would have been asking myself, why did to 10K resistor burn open? It feeds the 6L6 screen, and therefore a shorted output tibe may have been at fault. Was that 6L6 original, or a replacement? If original, it wont be trustworthy ( could have an intermittent short). I would also have checked the mains fuse, and HT fuse if it has one, because the incompetent previous servicer might have used incorrect fuse values. Finally, a shorted output tube, if thats what occured, can damage the heater supply balancing (centertap) resistors; they should have been checked for value and tolarance with an ohmmeter. Always best to ask "why?" rather than just replacung the obviouly damaged components.
HI There's a but more to this one than meets the eye apparently. See the comment from the guy who said Fender might have done that cut-track mod. No HT fuse with this one.
If so, I'm wondering if that smaller 22uF radial cap is actually still in circuit somehow and that's why adding another in parallel had no effect. Seems a bit of a mess from Fender tbh.
I did a lot o asking 'why' I felt. I may have come to the wrong concluion but I certainly had a theory about what had gone on.
I’m not convinced this amp is actually repaired. I’m curious what the idle current is. It shouldn’t take that much capacitance to reduce the hum.
Now I'll be singing "The 100Ω Blues" all night :(
Hi Don. It's a song that did real well for me in the 60's....
You really should reference a schematic…….
i think that jumper may actually have been a factory kludge.
It did look like the name Fender was on the circuit board, I reconised the F
Yes I completely missed that. I thought it was some unusual boutique amp!
Seems to me that maybe someone did some kind of bad mod to give the amp more gain.
Stuart 👍
Glad you enjoyed it Robbie.
A tech pro guy (Rat Valve Amp) talking about the buzz and Hum of this amp:
Another 'Issue' with the Stock Amp is the HIDEOUS Level of Background Noise (Severe Buzz and Hum).
There are three main problems:
(1) The Output Transformer (OPT) is too close to the Mains Transformer and Causes a Pronounced 'HUM' when the Amp is first switched on, even before it warms up - Simple Fix, Move the OPT away from the Mains Transformer - Done.
(2) Not enough Smoothing in the Power Supply which causes the Amp to 'BUZZ' - I have Corrected that.
(3) A Design Error on the Main PCB has caused an 'Earth Loop' in the Circuit, which is responsible for most of the Buzz and Hum in the Amp. Unbelievable in a Fender Amp and totally unacceptable.
Fender know there is a problem because they have made a 'Half-Ass' effort to correct it by cutting PCB Tracks here and there and adding lengths of wire to the Board, with no success. It took awhile to Find the Error, but I found it and corrected it.
The Result - The Amp is now 'SILENT' - NO Background Noise, it's so Quiet that it is difficult to tell if the Amp is On or Off."
So are you saying that cut track and black wire were Fender mods? I'd love to know what the error was that you found. The amp hum was just about acceptable but I'd like to get it lower if possible.
@@stuartukguitarampguy5830 Correct, that cut is from the factory. I don't have that amp, that notes are from the tech guy from Rat Valve Amp
@@nebojsatomic1210 Interesting and rather amazin!
@@stuartukguitarampguy5830 please let me know if you need a schematic
I can already tell the tubes have all gone bad because they are in jail.
You gotta get me outa here Mugsy...
@@stuartukguitarampguy5830
The slammer is too hot?
That big guy is the culprit. He is so arrogant they call him the power tube.
Interesting. Too late now, but try fender ramparte schematic on tdpri. A real schematic, allegedly, and also a forum (War and Peace) on fixing hum. The schematic (which may be rubbish of course) shows 1k for the resistor and only 416V on the first cap.
Hi Ralph,. ahh interesting can you be more specific about that link> I didnt recongise tdpri
Thanks
@@stuartukguitarampguy5830 Any comment with anything resembling a site gets pulled by YT (so infuriating and time wasting). Try the normal ending to tdpri. Then search, fender ramparte schematic, then the Blackstar post. I also sent stuff to your YT addr.