Hi
Ive recently bought a valvestate 8080, the amp was pretty beat up and had a buzz coming from the speaker.
Ive since cleaned it up, replaced all the caps, replaced most most of the the pots and also replaced all the ICs on the pre amp.
The transistors on the power amp I replaced with the following as the I cound not get hold of the old marshall T64,T65 also known as BDV65 and BDV64 in some models (TIP29C to replace TIP29CH , TIP172 to replace BDV65 and TIP147 to replace BDV64)
After I replaced all of those components and fired up the amp the fuse blew, stupid me did not use a light bulb limiter, after plugging into the limiter the flight didnt go on if the speaker were not plugged in, as soon as I connected the speaker the light would glow at full brightness. I installed the old marshall branded T64 and T65 transistors but the light would still go on after installing the old TIP29CH as well I had a working amp again.
I now have a working amp but I still have a buzz on the speaker, even if I disconnect the speaker I can hear the buzz, if I listen to were those transistors are installed at the heat sink I can hear a buzzing coming from that area.
I noticed that in the new transistors eg on old BDV65 I get a open reading when cheking base to emitter ut on the new TIP142 I can see that it is not open, I get a reading of 1.533, same goes for the BDV64, closed on B to E and on the replacement TIP 147 I get a reading of 1.888
Any ideas as to what is causing my amp to buzz? can those transistors make a mechanical buzzing sound if they are failing or old?
Please excuse my english and noobness when it comes to electronics.
Ive recently bought a valvestate 8080, the amp was pretty beat up and had a buzz coming from the speaker.
Ive since cleaned it up, replaced all the caps, replaced most most of the the pots and also replaced all the ICs on the pre amp.
The transistors on the power amp I replaced with the following as the I cound not get hold of the old marshall T64,T65 also known as BDV65 and BDV64 in some models (TIP29C to replace TIP29CH , TIP172 to replace BDV65 and TIP147 to replace BDV64)
After I replaced all of those components and fired up the amp the fuse blew, stupid me did not use a light bulb limiter, after plugging into the limiter the flight didnt go on if the speaker were not plugged in, as soon as I connected the speaker the light would glow at full brightness. I installed the old marshall branded T64 and T65 transistors but the light would still go on after installing the old TIP29CH as well I had a working amp again.
I now have a working amp but I still have a buzz on the speaker, even if I disconnect the speaker I can hear the buzz, if I listen to were those transistors are installed at the heat sink I can hear a buzzing coming from that area.
I noticed that in the new transistors eg on old BDV65 I get a open reading when cheking base to emitter ut on the new TIP142 I can see that it is not open, I get a reading of 1.533, same goes for the BDV64, closed on B to E and on the replacement TIP 147 I get a reading of 1.888
Any ideas as to what is causing my amp to buzz? can those transistors make a mechanical buzzing sound if they are failing or old?
Please excuse my english and noobness when it comes to electronics.
You have probably got loose laminations in the mains transformer. The transistors will not be noisy as they are failing. If they fail, that's it, short circuit.
Thanks gor response, would there be anything I can do to fix the transformer? or would I have to replace it.
Or a grounding issue. These can also make a mains transformer buzz and it would explain the buzz from the speakers and the difference it makes if a speaker is hooked up.
Ive have access to another valvestate 8080 that also does the exact same thing, buzzes with speaker connected and all dials set to 0 without anything plugged in and then still buzzes when speaker is disconnected.
It is a Marshall amp and prone to buzzing. I was referring to the buzz without a loudspeaker connected. With the speaker connected it will probably be an old smoothing capacitor issue but they all hum a little.
Actually, if it blows fuses when the speaker is attached, but not without a speaker, (or lights the bulb brightly rather than taking out a fuse) then most likely you have DC on the output. it is the presence of a load on that that draws the excess current.
Some power transformers hum mechanically, but that usually is not a problem.
Dinky, I urge you not to just randomly replace a lot of parts. Ever part you replace is another opportunity to make a bad solder connection or to inadvertently short two points together with stray solder. If you limit the part changing to things that really might be at fault, we limit these opportunities. Unless you have a reason to suspect an individual part, replacing all the ICs and non-electrolytic caps in the preamp is not necessary. Same with replacing old parts, then putting them back in.
Some power transformers hum mechanically, but that usually is not a problem.
Dinky, I urge you not to just randomly replace a lot of parts. Ever part you replace is another opportunity to make a bad solder connection or to inadvertently short two points together with stray solder. If you limit the part changing to things that really might be at fault, we limit these opportunities. Unless you have a reason to suspect an individual part, replacing all the ICs and non-electrolytic caps in the preamp is not necessary. Same with replacing old parts, then putting them back in.
Hey man, sure thing I wasnt replacing parts to fix anything, I just thought it might be good to replace the caps as the amp is very old and there was some really cheap caps in the amp taht who ever worked on it at some stage had but in as well as some cheap reistors that I had to replace with cement resistors, they get very very hot.
The amp is working 100% with the old transistors in the power amp. If I cant fix the buzz the amp has I suppose ill just have to live with it.
The last Marshall amp I bought had a terrible noise.
Turned out to be the cooling fan.
They are horrible cheap and nasty things.
I replaced it with one off ebay and it is very quiet now.
Here is a youtube video of one being replaced.
https://www.youtube.com/watch?v=fAKdrNAhV5w
Turned out to be the cooling fan.
They are horrible cheap and nasty things.
I replaced it with one off ebay and it is very quiet now.
Here is a youtube video of one being replaced.
https://www.youtube.com/watch?v=fAKdrNAhV5w
i cry every time i see someone become cursed with an 8080 amp...
not a marshall i'd consider to a reliable gigging amp (too many shortcomings in construction quality and imho a bad channel switching scheme not to mention all the likely hot resistors in the supply scheme that leaves a lot to be desired!)
not a marshall i'd consider to a reliable gigging amp (too many shortcomings in construction quality and imho a bad channel switching scheme not to mention all the likely hot resistors in the supply scheme that leaves a lot to be desired!)
I have a Marshall valve state amplifier and i wasnt that impressed with it.
It doesnt really give a proper valve sound.
I found the effects sound a bit washed out and thin.
They also weigh a ton to carry around.
Certainly useless for an upstairs gig. Would need 2 people to carry it upstairs.
I also have a 100 watt Marshall transistor amp.
I would prefer a pure valve Marshall amp but they are expensive even second hand.
It doesnt really give a proper valve sound.
I found the effects sound a bit washed out and thin.
They also weigh a ton to carry around.
Certainly useless for an upstairs gig. Would need 2 people to carry it upstairs.
I also have a 100 watt Marshall transistor amp.
I would prefer a pure valve Marshall amp but they are expensive even second hand.
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I didnt pay too much for the amp, it sounds good and all but the buzzing kinda sucks. I dont gig or anything, you think it would be best just to sell the amp rather than trying to get rid of the buzzing?
If I can find a decent sounding low wattage all tube marshall or marshall sounding amp ill get one, but its difficult to get low wattage affordable tube amps here in my country without spending a fortune or importing. I just recently wold my laney iron heart 60watt tube amp as it was waaaaay too loud for bedroom use and we all know u gota crank it to get those tubes working! otherwise it sounded too thin and fizzy for my liking.
If it has a toroidal transformer it might be DC on the mains causing the transformer to buzz. You can build your own DC killer circuit. Loads of circuits online.
Its not a toroidal transformer. Ill just pot the thing this week, doesnt seem like it can be anything else than magnetostriction. Ive heard about people solving the same issue by cleaning the transformers if they are old and rusty with some steel wool and giving it a polyurethane coat. seems like it should work.
No "coating" , just dunk the whole transformer in varnish and leave it there at least 2 hours, or preferrably overnight, until NO bubbles come out, meaning varnish got real deep (cover the can with a plastic bag and tie a string around it, so varnish does not evaporate needlessly) , then pull the transformer and hang it from a tree limb or whatever is available, put some newspaper under it and let it drip.
After at least one night drying, a full day even better, cut the "spiderwebs" hanging from it and remount it.
Will stink for a week every time you turn it on and it warms up, until all varnish fully dries, but ... who cares?
Factories vacuum impregnate in 5 minutes, and oven dry varnish in 30 , so wasting a couple nights at home is reasonable.
After at least one night drying, a full day even better, cut the "spiderwebs" hanging from it and remount it.
Will stink for a week every time you turn it on and it warms up, until all varnish fully dries, but ... who cares?
Factories vacuum impregnate in 5 minutes, and oven dry varnish in 30 , so wasting a couple nights at home is reasonable.
ok awesome haha damit I actually finished covering the thing with polyurethane just now! I poured it into the transformer, the middle part, as well so I hope it will be all good! Thanks for the advice if this fails Ill do your method as well over whats already on the transformer now.
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@ JMFahey What varnish would you recommend? Is there not a chance of the transformer catching on fire? All my varnish is flammable.
In fact *all* kinds of solvent based varnishes are flammable, because solvents are ... that's why you let it drip and air dry at least overnight and preferrably a day.
Best of course is a specific use transformer varnish.
That said, many (even some transformer makers 😉 ) just use some good quality general purpose varnish, suitable for wood surfaces and even iron structures.
Get a Tupperware type rectangular pot where transformer just fits in, or as close as possible, so it occupies most of the space and you need less varnish to cover it.
If you use a liter, transformer will just absorb 1/10th of that, but you need the full liter to completely cover the transformer.
Whatever's left over afterwards (which is a lot) can be used for the regular purpose, generally furniture, wood walls or floors, etc. so actual expense is very little.
You can use the so called "Marine" varnish.
Whay you need is the regular kind, single component, air dry.
2 component (varnish + hardener) Epoxy or Polyurethane is *excellent* but any unused leftover will be lost, as it gellifies and hardens.
Best of course is a specific use transformer varnish.
That said, many (even some transformer makers 😉 ) just use some good quality general purpose varnish, suitable for wood surfaces and even iron structures.
Get a Tupperware type rectangular pot where transformer just fits in, or as close as possible, so it occupies most of the space and you need less varnish to cover it.
If you use a liter, transformer will just absorb 1/10th of that, but you need the full liter to completely cover the transformer.
Whatever's left over afterwards (which is a lot) can be used for the regular purpose, generally furniture, wood walls or floors, etc. so actual expense is very little.
You can use the so called "Marine" varnish.
Whay you need is the regular kind, single component, air dry.
2 component (varnish + hardener) Epoxy or Polyurethane is *excellent* but any unused leftover will be lost, as it gellifies and hardens.
Ive gotten a can of varnish that ill use for that! awesome yes ill use a container like you mentioned and fill it up so the terminals just stick out.
I will only do this if my polyurethane potting compound didnt cure the buzz.
I used this tuff
FR974C1-250 - RESIN POTTING COMPOUND 250g
Yes true I had to throw away alot of this stuff, It got thick really quick, only usable for about 15- 20 mins.
The varnish method you have sounds way better, less messy and not wasteful like you said!
I can see there was some form of varnish on this transformer at one stage of its life, but its worn off somehow! Fingers crossed that ive fixed the thing now! Ill install it back into the amp later tonight and hope it doesnt burn my house down.
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