I bet Leo never dreamed his amps would be so cherished and so well cared for over 60 years from when they left the factory, you get a thumbs-up and a medal 🏅just for taking pride in your work and listening to the customer.
Very smart to replace all the Astron caps. Unless an amp is going into a museum, getting to a safe, robust, reliable, great sounding amp should be the goal. As others have said, capacitors, resistors, and tubes were meant to be replaceable components. Nice to see the honest approach here! BTW if buying a vintage Fender, I would rather have new Vishay caps visible, rather than stuffed Astrons - same with the electrolytic caps. Stuff your Poblano Chiles instead.
We were going for the all original look in the amp, but I get it. To make it VERY clear in the doghouse there's a note saying they're stuffed with Sprague pointing to my YT channel to see the work done.
@@YeatzeeGuitar Yup - understood. And if that is what the amp owner wants - that's the way to get there. It's just never been a concern of mine, but I love stuffed Poblanos🙂 You are doing good work and explaining things well. The guitar and amp world is a funny one. People want their guitars reliced and their amps to look new. I'm holding my ratty tweed Fenders until reliced amps become a thing.
Your transparency and honesty is a good way to go. Thanks for being humble, we ALL make mistakes...what does Einstein say...anyone who has never made a mistake has never tried anything new. Side note, your video production is very good.
To test coupling caps for leakage, I've seen some techs use a heat gun to warm up the cap while measuring the dc. If it rises, the cap is going to leak more dc when the amp gets hot. But as you've concluded, it's probably safer just to replace them.
Build a cap leakage tester,they are simple to build,I did and they work great,you can't test electrolytic caps with them,but you can reform electrolytic caps with them,I wouldn't bother reforming any electrolytic cap anyway.
To an extent, I understand originality, but I also know that Leo was notorious for choosing the cheapest parts available... So, arguably, the originals may not have even been ideally functioning parts. A new, fully functioning part is always preferable to a compromised original. 98% of the sound of a circuit is in the configuration + actual measured values of the components. Not a specific polyester film capacitor or carbon composite resistor
It's a compromise of course, in the same way keeping old carbon comps are a compromise. They're going to have a tendency of being noisier, and more fickle plus natural resistance drift. Why not just gut the amp and replace every single one with metal oxides? It'll be far more reliable right..
I honestly think they'll be fine, it's going to get some long testing this weekend to confirm it's showing no signs of anything and I'll be using those tubes to be sure. So far though, they've been rock solid. Those old 5881's are tough.
ESR (equivalent SERIES resistance) does not apply in this situation. Of concern is Insulation resistance (PARRALLEL or Shut resistance). Generally in tube amps (with linear power supplies) ESR is not a huge problem and measuring unknown electrolytics can be misleading without a reference measurement. Modern e-caps likely have low ESR and lower than vintage types even when they were new.
Something still does not seem right. As you say, even after idling for 2 hours, you were nowhere near Red Plating. Is it possible the owners wall supply was real high.? I have seen ours get to 132 VAC. If you are at 123........ 🙂 But yeah, what else was left but the Astrons..? They are not long for this world, and should be replaced (probably) on sight At any rate...... Job Well Done 🙂
I agree. Attention and testing needs to be done under dynamic conditions. Confirm the PI is balanced with in reason. Also severe blocking distortion can cause red plating. PI to speaker and back through inverse feedback loop is all suspect till you prove the failure mode and at times it's helpful to open the nfb loop when troubleshooting so you have a linear direction of circuit so to speak, to work with.
Your efforts are appreciated, but you don't have a time machine. The original mylar film is just too degraded to trust now. Even the 200v Astrons used in tone and presence controls are pretty much bad by now. Owners have to decide if they want a museum piece to be looked at, which it had better be in mint condition OR do they want to use their Tweed/Brown amps. I vote use. Jupiter's are my preferred cap for these amps. The MKT's are great caps, but they're metallized film. Jupiter's are actual aluminum foil and mylar.
Thanks Matt. Stay tuned, next video there's a little mini comparison of jupiter vs mkt. Too expensive to but all the former, but owner was curious so he bought two to try.
@ 460 pv your current draw should be just about 40 MA per tube @ 70% dissipation . if your draw has larger differential with tubes in it. it's like ly because once you ve red plated one the match between the two checks out.. try a fresh pair. & good luck.
@@YeatzeeGuitar whose brand of 5881's were you using?. i only ask because some techs claim for certain 5881's (jj;s probably) 460pv.is beyond whats comfortable.. if they robust, sovtek's etc you should be ok.. i think the schematic for the super 6g4-a circuit which I think is what you had calls out 450v W 5881's.. iv'e used the russian 6p3s-E which is a ruggedized 5881 im using them in a 5f6a @ 415 pv & have heard some say 475 pv = no worries..
@@Gorilla.Guitar Vintage. Yeah this era bigger amps used 5881's all with plate voltages in that range. Concert is another one, probably even higher than this. I'd sooner just go to modern 6l6's if using a new tube.
@@YeatzeeGuitar been chasing this stuff as a hobby for few years, just my own stuff. theres a lot of good people in the community that have a wealth of knowledge to share. which is how i stumbled upon your channel. you definitely have your customer service skills on point I believe you claim to be relatively new at it (?) most have good knowledge but the techniques can vary. which is what I try to determine. pay attention & remember the good ideas. you most likely know what You Tube channels are worthy but i'll pass 'em along just in case *Uncle Doug*.- great channel mostly restores hand wired fenders, great explanation, concise, expert level repair. i've actually catalogued a lot of his content that i didn't understand at viewing time & have gone back to for clarification... Psionic Audio- good stuff, more variety in brands & types of repair. his personality is a bit ogre-ish but he's a wealth of knowledge as well.. then there's the guitologist.. have a fire extinguisher handy for that one. keep up the good work!
@@YeatzeeGuitar, Tungsol 588I's from the 1950s were purportedly designed during the Cold War for the military, to drive the servo motors for bombsights on planes. The originals are extremely rugged, and can certainly handle more than their official 430v, 23 watt rating. Modern Russian and Chinese tubes are another matter entirely.
im confused about some things..You claim to have re-stuffed all the old electrolytics w/new. So the caps that say ASTRON have a different capacitor stuffed in them? if so, are they no good as well? brand? you can lift the output side of caps in circuit & test for DC leakage the accepted practice is yellow astrons straight to trash, do not pass go.. the blue astrons are much nicer, holding their UF rating for decades. 460v is hot for some 5881's try dropping closer to 400-410pv.or possibly substitute a 5u4g rectifier, assuming theres enough current supply.
Bypass caps = stuffed, coupling caps obviously are original and untouched. I've only ever seen one person stuff yellow astrons, I tried once and it was too brittle and fell apart.
Caps are a serviceable part so why not change them? Ridiculous to leave old crappy caps in a fantastic vintage amp. Get some F&T's in there and forget it for 30 years!
There always has to be one jerk, sad! Like Tanner said, blue molded caps are almost as old and usually test fine. Before you post an ignorant comment, learn your amp stuff cause you just showed you know nothing about amps. Tanner, please ignore people like this. Love the channel, can't wait for the next video!
Say it with me! NEVER TRUST AN ASTRON! 👊
I bet you could stuff those astrons.
He's a real man! Integrity; tells the truth; corrects the issue; apologizes where needed even though this was an honest mistake. Good work!
I bet Leo never dreamed his amps would be so cherished and so well cared for over 60 years from when they left the factory, you get a thumbs-up and a medal 🏅just for taking pride in your work and listening to the customer.
🙏 Thanks!
Very smart to replace all the Astron caps. Unless an amp is going into a museum, getting to a safe, robust, reliable, great sounding amp should be the goal. As others have said, capacitors, resistors, and tubes were meant to be replaceable components. Nice to see the honest approach here! BTW if buying a vintage Fender, I would rather have new Vishay caps visible, rather than stuffed Astrons - same with the electrolytic caps. Stuff your Poblano Chiles instead.
We were going for the all original look in the amp, but I get it. To make it VERY clear in the doghouse there's a note saying they're stuffed with Sprague pointing to my YT channel to see the work done.
@@YeatzeeGuitar Yup - understood. And if that is what the amp owner wants - that's the way to get there. It's just never been a concern of mine, but I love stuffed Poblanos🙂 You are doing good work and explaining things well. The guitar and amp world is a funny one. People want their guitars reliced and their amps to look new. I'm holding my ratty tweed Fenders until reliced amps become a thing.
@@brianmccowan1949 fender has done relic amps in the past! Nothing cooler than a ratty tweed imo
Your transparency and honesty is a good way to go. Thanks for being humble, we ALL make mistakes...what does Einstein say...anyone who has never made a mistake has never tried anything new. Side note, your video production is very good.
To test coupling caps for leakage, I've seen some techs use a heat gun to warm up the cap while measuring the dc. If it rises, the cap is going to leak more dc when the amp gets hot. But as you've concluded, it's probably safer just to replace them.
I like that trick!
Build a cap leakage tester,they are simple to build,I did and they work great,you can't test electrolytic caps with them,but you can reform electrolytic caps with them,I wouldn't bother reforming any electrolytic cap anyway.
To an extent, I understand originality, but I also know that Leo was notorious for choosing the cheapest parts available... So, arguably, the originals may not have even been ideally functioning parts. A new, fully functioning part is always preferable to a compromised original. 98% of the sound of a circuit is in the configuration + actual measured values of the components. Not a specific polyester film capacitor or carbon composite resistor
It's a compromise of course, in the same way keeping old carbon comps are a compromise. They're going to have a tendency of being noisier, and more fickle plus natural resistance drift. Why not just gut the amp and replace every single one with metal oxides? It'll be far more reliable right..
Same with Sangamo caps.
No apologies needed man. We took a chance and no dice. Oh well. I do have an uneducated concern though… since the tubes red plated… are they ok?
I honestly think they'll be fine, it's going to get some long testing this weekend to confirm it's showing no signs of anything and I'll be using those tubes to be sure. So far though, they've been rock solid. Those old 5881's are tough.
Jupiter caps would look the part expensive, but good caps. Do you have an ESR meter? Might be handy.
Do not!
ESR (equivalent SERIES resistance) does not apply in this situation. Of concern is Insulation resistance (PARRALLEL or Shut resistance). Generally in tube amps (with linear power supplies) ESR is not a huge problem and measuring unknown electrolytics can be misleading without a reference measurement. Modern e-caps likely have low ESR and lower than vintage types even when they were new.
Something still does not seem right.
As you say, even after idling for 2 hours, you were nowhere near Red Plating.
Is it possible the owners wall supply was real high.?
I have seen ours get to 132 VAC.
If you are at 123........ 🙂
But yeah, what else was left but the Astrons..?
They are not long for this world, and should be replaced (probably) on sight
At any rate...... Job Well Done 🙂
You're not wrong, spoiler alert but the problem aint fixed!
I agree. Attention and testing needs to be done under dynamic conditions. Confirm the PI is balanced with in reason. Also severe blocking distortion can cause red plating. PI to speaker and back through inverse feedback loop is all suspect till you prove the failure mode and at times it's helpful to open the nfb loop when troubleshooting so you have a linear direction of circuit so to speak, to work with.
Your efforts are appreciated, but you don't have a time machine. The original mylar film is just too degraded to trust now. Even the 200v Astrons used in tone and presence controls are pretty much bad by now.
Owners have to decide if they want a museum piece to be looked at, which it had better be in mint condition OR do they want to use their Tweed/Brown amps.
I vote use. Jupiter's are my preferred cap for these amps. The MKT's are great caps, but they're metallized film. Jupiter's are actual aluminum foil and mylar.
Thanks Matt. Stay tuned, next video there's a little mini comparison of jupiter vs mkt. Too expensive to but all the former, but owner was curious so he bought two to try.
Yellow astrons and green sangamo's. Both are always kaput
Also, "Pyramid"-brand capacitors. And then there are the Bumblebees.....😖
Have they started producing the yellow aston replicas yet? I saw an advertisement somewhere a while back.
@@huddyskiba1 I haven't seen anything about those in a while. Would be great, I tried stuffing one and it shattered. Super fragile and brittle.
@ 460 pv your current draw should be just about 40 MA per tube @ 70% dissipation . if your draw has larger differential with tubes in it. it's like ly because once you ve red plated one the match between the two checks out.. try a fresh pair. & good luck.
I typically bias fenders cooler than 70%. Closer to 60% is more my preference. The first bias measurements were with my own set of matched 5881's.
@@YeatzeeGuitar whose brand of 5881's were you using?. i only ask because some techs claim for certain 5881's (jj;s probably) 460pv.is beyond whats comfortable.. if they robust, sovtek's etc you should be ok.. i think the schematic for the super 6g4-a circuit which I think is what you had calls out 450v W 5881's.. iv'e used the russian 6p3s-E which is a ruggedized 5881 im using them in a 5f6a @ 415 pv & have heard some say 475 pv = no worries..
@@Gorilla.Guitar Vintage. Yeah this era bigger amps used 5881's all with plate voltages in that range. Concert is another one, probably even higher than this. I'd sooner just go to modern 6l6's if using a new tube.
@@YeatzeeGuitar been chasing this stuff as a hobby for few years, just my own stuff. theres a lot of good people in the community that have a wealth of knowledge to share. which is how i stumbled upon your channel. you definitely have your customer service skills on point I believe you claim to be relatively new at it (?) most have good knowledge but the techniques can vary. which is what I try to determine. pay attention & remember the good ideas. you most likely know what You Tube channels are worthy but i'll pass 'em along just in case *Uncle Doug*.- great channel mostly restores hand wired fenders, great explanation, concise, expert level repair. i've actually catalogued a lot of his content that i didn't understand at viewing time & have gone back to for clarification... Psionic Audio- good stuff, more variety in brands & types of repair. his personality is a bit ogre-ish but he's a wealth of knowledge as well.. then there's the guitologist.. have a fire extinguisher handy for that one. keep up the good work!
@@YeatzeeGuitar, Tungsol 588I's from the 1950s were purportedly designed during the Cold War for the military, to drive the servo motors for bombsights on planes. The originals are extremely rugged, and can certainly handle more than their official 430v, 23 watt rating. Modern Russian and Chinese tubes are another matter entirely.
Not worth the risk. Not your fault, but great customer service.
Do you still have the Princeton 64 ?
The handwired? No I sold it a while back
im confused about some things..You claim to have re-stuffed all the old electrolytics w/new. So the caps that say ASTRON have a different capacitor stuffed in them? if so, are they no good as well? brand? you can lift the output side of caps in circuit & test for DC leakage the accepted practice is yellow astrons straight to trash, do not pass go.. the blue astrons are much nicer, holding their UF rating for decades. 460v is hot for some 5881's try dropping closer to 400-410pv.or possibly substitute a 5u4g rectifier, assuming theres enough current supply.
Bypass caps = stuffed, coupling caps obviously are original and untouched. I've only ever seen one person stuff yellow astrons, I tried once and it was too brittle and fell apart.
Caps are a serviceable part so why not change them? Ridiculous to leave old crappy caps in a fantastic vintage amp.
Get some F&T's in there and forget it for 30 years!
The electrolytics were already swapped with Sprague, they're just stuffed inside the original shells..
Did it ever cross your mind?That maybe seventy year old capacitors might be a bad fucking idea fucking duh
Those blue moldeds are the same age and fine. But thanks for the nice comment.
There always has to be one jerk, sad! Like Tanner said, blue molded caps are almost as old and usually test fine. Before you post an ignorant comment, learn your amp stuff cause you just showed you know nothing about amps.
Tanner, please ignore people like this. Love the channel, can't wait for the next video!