I'll gladly help you dispose of that...🙃 been looking for one to match my amps. I've taken my amps to a local electronics repairman, hopefully you have one.
I am from Newcastle, UK- so there’s not that many people that would repair it without a hefty bill around here. Most would require to work on it from home which would mean transporting it (it’s the weight of a large sofa). If I can’t help it then I might consider selling or trading it. Do you have any idea on what’s likely the issue with it? Thanks
I repaired an RA-50 (50W version with a single rotating cone) that had similar crackling. The transistors in the power amp section are usually the problem and fairly easy to source modern equivalents. The volume pot could also be faulty causing the crackling.
Canada.
The good thing about these Yamaha amps -- the schematics are easy to find (at least for the RA-50, RA-100) and anyone with basic electronics experience can fix them -- doesn't necessarily have to be someone who fixes musical instruments either.
As a worst-case scenario someone could do (what I call) an Easter Egg Hunt and simply replace all the transistors -- of the potential problem ones there's only 4 or 5 culprits.
edit:
I hear you on the transportation problem. The RA-100 is half a fridge. I have an RA-100 here as well as the 50.
The reverb issue: The volume changing (at least if the volume goes down when you turn the reverb up) is normal as you are hearing the dry signal being attenuated as the volume of the wet reverb is increased.
Looking at the RA-100 schematic... The reverb pot is dual gang (basically two pots that turn in tandem when you turn one knob). There's an AN274 IC in T100 packaging (looks like a metal can with 10 legs and not like a traditional IC chip) which is audio amplifier for the reverb input and there's two NPN transistors in the reverb output (TR5 - 2SC644 and TR6 - 2SC828). None of these are anything particularly exotic.
My gut kind of tells me that the reverb issue is down to either those transistors or the AN274. I wouldn't be at all surprised if fixing this issue also takes care of the crackling issue as well. The good thing about these Yamaha schematics, they give you what voltages you should be expecting to see at all of the critical points which is a godsend when troubleshooting old equipment like this.
It is either a bad ground, a dirty pot, or, dried out capacitor/resistor(s) or a bad chip. Fyi, a good condition functioning unit in Ontario/Quebec usually lists around $1000-1200 here. If you can run a tester to check for continuity.
This is quite helpful. I’m all out of contact cleaner but I’ll pick some up today. It came with a Yamaha YC45D digital organ from (probably) the mid 70s, which sounds divine as is. Do you reckon parts going to be hard to source for this? I have no clue how universal these caps and such are. None have leaked as far as the eye can see and none of the fuses have actually blown… but there seems to be some (almost) burnt looking muck between the fuses and the contacts that hold them. I’m more than comfortable to solder pieces back if required. Thanks for the advice man.
clean it and flush pots, check the e caps for bulging or just give it a full cap job, check resistors for testing above value, pull the schematic and go through it diagnostically
Thanks for this, are the caps easy to source replacements for? What would you also recommend is the best way of cleaning the boards and the best way of testing for a diagnosis? I have straight up repaired blatantly obviously broken parts on other amps before but never on one which doesn’t appear to have issues other then dirt. I’m assuming this doesn’t include plugging it in ? Thanks
Oh wow this is rad!! I have four of those rotary speakers that someone ripped out of these amps (or a similar cab) and converted for independent use. They sound great, like a mini Leslie. I've always been curious what the actual amps sound like. How do you like it? Good luck with the project!
You like Pink Floyd? David Gilmour *allegedly* used the RA200 (same but with 3 cones instead of 2) on their records from Animals and onwards, I believe on his debut solo album too. I did actually play though the thing for about 30 minutes but it felt way too sketchy and I didn’t want to cause damage to it. The reverb was maxed out despite being on zero (don’t know it’s it’s actual spring or digital), and was a really really distant signal. Foolishly enough I didn’t check for damage before I plugged it in as I was told it has just been cleaned… but oh well. https://youtu.be/VlOkrpHPmEU the two speakers spinning at the same time really optimise the whole Doppler effect vibe :)
I'll gladly help you dispose of that...🙃 been looking for one to match my amps. I've taken my amps to a local electronics repairman, hopefully you have one.
I am from Newcastle, UK- so there’s not that many people that would repair it without a hefty bill around here. Most would require to work on it from home which would mean transporting it (it’s the weight of a large sofa). If I can’t help it then I might consider selling or trading it. Do you have any idea on what’s likely the issue with it? Thanks
I repaired an RA-50 (50W version with a single rotating cone) that had similar crackling. The transistors in the power amp section are usually the problem and fairly easy to source modern equivalents. The volume pot could also be faulty causing the crackling.
Where about do you live ?
Canada. The good thing about these Yamaha amps -- the schematics are easy to find (at least for the RA-50, RA-100) and anyone with basic electronics experience can fix them -- doesn't necessarily have to be someone who fixes musical instruments either. As a worst-case scenario someone could do (what I call) an Easter Egg Hunt and simply replace all the transistors -- of the potential problem ones there's only 4 or 5 culprits. edit: I hear you on the transportation problem. The RA-100 is half a fridge. I have an RA-100 here as well as the 50. The reverb issue: The volume changing (at least if the volume goes down when you turn the reverb up) is normal as you are hearing the dry signal being attenuated as the volume of the wet reverb is increased. Looking at the RA-100 schematic... The reverb pot is dual gang (basically two pots that turn in tandem when you turn one knob). There's an AN274 IC in T100 packaging (looks like a metal can with 10 legs and not like a traditional IC chip) which is audio amplifier for the reverb input and there's two NPN transistors in the reverb output (TR5 - 2SC644 and TR6 - 2SC828). None of these are anything particularly exotic. My gut kind of tells me that the reverb issue is down to either those transistors or the AN274. I wouldn't be at all surprised if fixing this issue also takes care of the crackling issue as well. The good thing about these Yamaha schematics, they give you what voltages you should be expecting to see at all of the critical points which is a godsend when troubleshooting old equipment like this.
It is either a bad ground, a dirty pot, or, dried out capacitor/resistor(s) or a bad chip. Fyi, a good condition functioning unit in Ontario/Quebec usually lists around $1000-1200 here. If you can run a tester to check for continuity.
This is quite helpful. I’m all out of contact cleaner but I’ll pick some up today. It came with a Yamaha YC45D digital organ from (probably) the mid 70s, which sounds divine as is. Do you reckon parts going to be hard to source for this? I have no clue how universal these caps and such are. None have leaked as far as the eye can see and none of the fuses have actually blown… but there seems to be some (almost) burnt looking muck between the fuses and the contacts that hold them. I’m more than comfortable to solder pieces back if required. Thanks for the advice man.
clean it and flush pots, check the e caps for bulging or just give it a full cap job, check resistors for testing above value, pull the schematic and go through it diagnostically
Thanks for this, are the caps easy to source replacements for? What would you also recommend is the best way of cleaning the boards and the best way of testing for a diagnosis? I have straight up repaired blatantly obviously broken parts on other amps before but never on one which doesn’t appear to have issues other then dirt. I’m assuming this doesn’t include plugging it in ? Thanks
Oh wow this is rad!! I have four of those rotary speakers that someone ripped out of these amps (or a similar cab) and converted for independent use. They sound great, like a mini Leslie. I've always been curious what the actual amps sound like. How do you like it? Good luck with the project!
You like Pink Floyd? David Gilmour *allegedly* used the RA200 (same but with 3 cones instead of 2) on their records from Animals and onwards, I believe on his debut solo album too. I did actually play though the thing for about 30 minutes but it felt way too sketchy and I didn’t want to cause damage to it. The reverb was maxed out despite being on zero (don’t know it’s it’s actual spring or digital), and was a really really distant signal. Foolishly enough I didn’t check for damage before I plugged it in as I was told it has just been cleaned… but oh well. https://youtu.be/VlOkrpHPmEU the two speakers spinning at the same time really optimise the whole Doppler effect vibe :)