Music Man Power Supply [was Re: #102 died yesterday :( how,why]

[Aaron]

Looks good Aaron! I don't know how accurate you want to draw that up but the resistors looks to be a combination of the Sprague Q-lines (tan) Phiers (RED) and Dale's RN65's (Plates) If you don't want to color every resistor maybe at least make a note on the Layout is always a nice touch This is the normal Dumble fare.
BTW. Visio layouts are very time consuming I know They are by far IMO the best looking! IMO!

Thanks
Tony

I’m happy to go as accurate to the amp. I’ll have to get a new mouse though. I was using one of the kids and it’s about half the size, so my hand was starting to cramp
Looking back at it now, the wiring is a bit messy too.
I can make a start with the colour coding over the weekend. I’ve got work tonight.
Thanks,
Aaron

[talbany]

Looks good Aaron! I don't know how accurate you want to draw that up but the resistors looks to be a combination of the Sprague Q-lines (tan) Phiers (RED) and Dale's RN65's (Plates) If you don't want to color every resistor maybe at least make a note on the Layout is always a nice touch This is the normal Dumble fare.
BTW. Visio layouts are very time consuming I know They are by far IMO the best looking! IMO!

Thanks
Tony

I’m happy to go as accurate to the amp. I’ll have to get a new mouse though. I was using one of the kids and it’s about half the size, so my hand was starting to cramp
Looking back at it now, the wiring is a bit messy too.
I can make a start with the colour coding over the weekend. I’ve got work tonight.

Aaron

Awesome!. If you take a look at the photo copys of the amp the (light color) ones that have the protruding end caps are the Q-Lines. These look to be the most used and are throughout the entire amp. The Dark color ones are going to be the Phiers. There are a few scattered here and there. The Skinny resistors are more than likely the Dales (Plates) .. It's hard to say for sure but the MF (Skinny) Bypass resistors could be the IRC's and these are grey.
Let me know if I can help further!
Thanks and take care of that hand Tony

[Bombacaototal]

I’m not buying it. I can see some HF noise being generated, but “feel?” How does that work?

Sure That "HF" noise can generate "spikes" in the top end (AC cycle is going through the zero-line)Riding on the supply voltage can affect how the amp sounds and in some cases how the top end feels.. Some well respected builders even prefer to go with a Uf5804 (Fuchs, Two Rock)to help smooth out those spikes and help prevent a buzzy-ness riding on the top end.

Tony

I was going through the diodes topic. The BY448 I used seems to be a standard recovery diode, as is the 1N4007 (I assume there won't be much difference between the two?). The UF504 is an Ultra Fast Recovery, I am curious to try this in the future. Which is your favourite Tony?

[martin manning]

I'm still not buying it, BTW. Even the Hi-Fi guys argue over whether fast recovery vs. ordinary rectifiers in the power supply makes any difference at all. Use fast recovery diodes if you want to, they are only pennies more than standard.

[Mr. dB]

I’d have to check the accuracy of my LTSpice EF86 models I use again. Last time I checked the curves were pretty much spot on the curves in the Philips datasheet. I hold the Ayumi models in high regard. Usually I’m not more than 5 to 10% max off when comparing sims to real life. I think the 240k anode resistor is wrong there. Must admit though that I need to draw some load lines in the datasheet to confirm what spice is telling me. Anyways, simmed my hifi amps too, 2x ef184 phase inverter and it was very accurate.

Busy day today, will look into the recent posts better when I get home.

By the way: anyone willing to do an accurate Visio layout, so we can compare to the blurry shots we have?

By the way 2: where is that parts list? I must have missed it somehow.

Updated schematic below.

The parts list are on previous posts on this thread, there are some from Tony and some from me. I mapped all the parts and their respective numbers to my schematic.

I started the layour on .DIY, will share as soon as there is progress

Thanks for all the work you've put into this, and for sharing it.

I'm curious why a 12AX7 for the cathode follower?

[Bombacaototal]

No problem, always glad to help. It’s the typical SSS PI arrangement, with 2x12AX7

[Bombacaototal]

So, I bought a couple of the mojotone 7020320 Filament Power Transformer with Cover 120-220-230V 6.3v at 4A. One of which to use on the Alligator.

The second is for an older amp. When working on the tracing of the Alligator I realised one of my older amps was running a 4.5A current on a 4A transformer. To be honest I never noticed any issues with this amp. What would be the “to expect” in a scenario like this? Anyway I thought it would be a good approach to run the supplementary transformer, but I didn’t realise how big it actually is. I was expecting something in the size of a choke or maybe a reverb transformer but it is way bigger. Now I am wondering if I should just leave the amp as is (given it never had issues) running 4.5A at 4A or if I should try to squeeze this transformer in (for best practices).

[norburybrook]

So, I bought a couple of the mojotone 7020320 Filament Power Transformer with Cover 120-220-230V 6.3v at 4A. One of which to use on the Alligator.

The second is for an older amp. When working on the tracing of the Alligator I realised one of my older amps was running a 4.5A current on a 4A transformer. To be honest I never noticed any issues with this amp. What would be the “to expect” in a scenario like this? Anyway I thought it would be a good approach to run the supplementary transformer, but I didn’t realise how big it actually is. I was expecting something in the size of a choke or maybe a reverb transformer but it is way bigger. Now I am wondering if I should just leave the amp as is (given it never had issues) running 4.5A at 4A or if I should try to squeeze this transformer in (for best practices).

Leave it until it explodes

I would imagine unless your running it every night at loud gig levels it will be fine.


M

[donvan]

So, I bought a couple of the mojotone 7020320 Filament Power Transformer with Cover 120-220-230V 6.3v at 4A. One of which to use on the Alligator.

The second is for an older amp. When working on the tracing of the Alligator I realised one of my older amps was running a 4.5A current on a 4A transformer. To be honest I never noticed any issues with this amp. What would be the “to expect” in a scenario like this? Anyway I thought it would be a good approach to run the supplementary transformer, but I didn’t realise how big it actually is. I was expecting something in the size of a choke or maybe a reverb transformer but it is way bigger. Now I am wondering if I should just leave the amp as is (given it never had issues) running 4.5A at 4A or if I should try to squeeze this transformer in (for best practices).

Leave it until it explodes

I would imagine unless your running it every night at loud gig levels it will be fine.


M

I don't think that the level that the amp is running has a lot of affect on the filament current. There are some amps where Dumble exceeded the filament current on his amps but maybe he knew that his transformers were over-speced. Since I'm not Dumble, I would not feel good at all using a 4A transformer that is running 4.5A. Why risk fire or other potential damage to your amp?
Just my 2 cents.

[Bombacaototal]

Thanks Donvan and Marcus for the advice, I will go for the external filament transformer. Will at least give peace of mind ...and I bought them already, might as well use it...

[norburybrook]

So, I bought a couple of the mojotone 7020320 Filament Power Transformer with Cover 120-220-230V 6.3v at 4A. One of which to use on the Alligator.

The second is for an older amp. When working on the tracing of the Alligator I realised one of my older amps was running a 4.5A current on a 4A transformer. To be honest I never noticed any issues with this amp. What would be the “to expect” in a scenario like this? Anyway I thought it would be a good approach to run the supplementary transformer, but I didn’t realise how big it actually is. I was expecting something in the size of a choke or maybe a reverb transformer but it is way bigger. Now I am wondering if I should just leave the amp as is (given it never had issues) running 4.5A at 4A or if I should try to squeeze this transformer in (for best practices).

Leave it until it explodes

I would imagine unless your running it every night at loud gig levels it will be fine.


M

I don't think that the level that the amp is running has a lot of affect on the filament current. There are some amps where Dumble exceeded the filament current on his amps but maybe he knew that his transformers were over-speced. Since I'm not Dumble, I would not feel good at all using a 4A transformer that is running 4.5A. Why risk fire or other potential damage to your amp?
Just my 2 cents.

I like a bit of drama sparks, fire, all adds to the fun


M

[donvan]

I like a bit of drama sparks, fire, all adds to the fun
M

Ha! I can't argue with that.

[Bombacaototal]

I was wondering if there may be any reason why had might have chosen 150R for the supplementary filament rather than 100R?

[donvan]

I was wondering if there may be any reason why had might have chosen 150R for the supplementary filament rather than 100R?

I'm not sure why he chose 150R. Assuming your are talking about the artificial center tap, per the following link, 100 - 220 is typical. Whatever you chose, just calculate the current draw and use the correct resister power rating 1/4 or 1/2 watt.
http://www.valvewizard.co.uk/heater.html

[Bombacaototal]

Thanks Donvan, very helpful.

I am on a bit of a scratching head situation. My amp has a 240V/230V/220V switch. The mains in central London are usually between 246V and 253V and therefore I have been running the amp at 240V. I like the option of been able to lower if travelling to a place were mains are running low, for example sub 220V. The mojotone supplementary transformer onle has 230V/220V taps. I was thinking in hardwiring it at 230V, but with the high mains in UK it will (i) lose around 250mA of current and (ii) increase the secondary voltage. In the first case there should be no problem as I will be using around 2.5A our of the 4A available, but the secondary is where the headache starts. I think I may need to drop secondary voltage if going straight from the mains in the UK (via resistors as per article linked by donvan), but then if going to mainland EU where mains are between 228V and 235V will get the secondary maybe too low? And what about a sub 220V scenario? Any suggestions on a work around this with the transformers I currently have?

The easier option would be to replace my bassman transformer by a twin transformer which will give me plenty of current, but there is the extra cost of getting a new transformer..and all the work in swapping everything....other option would be to find a supplementary filament transformer with 240V/230V/220V ...