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power amp experts, thoughts on this 1000w beast!

Ordering the nichicon caps from mouser today. any other components worth getting? Not sure what make they are, but someone commented on those red/yellow/white striped caps (C17/C17b) thoughts?

Btw when comparing circuit diagram with the boards, I found some differences, so going with the actual circuits. The differences are: C15/16 are 10/40 EKU's, C5/6 are 4.7/40 EKU's, C7 is 22/16.

I guess going up on the voltage a bit is not a bad thing to do?

My BoM looks like this:
uF/V type Qty position
10/50 ES 8 C15/16
4.7/40 ES 16 C1/3/5/6
22/25 ES 4 C7
47/50 ES 8 C4/25
47/63 FG 8 C9/24
 
The striped capacitors look like the old Mullard Tropical fish Polyester type, unless they are physically damaged by heat they should all be OK
Can be replaced by a new Polyeter, Polystyrene or Polypropylene depending on value.

For the main power supply caps I would disconnect each one and test them for Capacitence and ESR
Don't forget to change the Bridge rectifiers
Alan
 
Very interesting design as it's basically the MF A370 with BJT's rather than mosfets but seems to pre-date the MF amp... I'd always thought TdP had nicked the basic circuit from a Motorola app note.. hmm...

Unfortunately the way it's done here is optimised for cool running and loads of power and distortion is likely to be quite high, especially at HF, plus I'd expect crossover artefacts present.

Glen at Alchemist built something similar at home and brought it in out of the blue one day then took it home that night... It sounded great!
 
That does look like a nice find. The advice about capacitors seems sensible, just annoying that you have to spend money to decide whether it's worth spending money on - oh well!

As for changing the XLRs for Speakon, that looks like a possible, I think the XLRs look to have the standard 25*30mm rectangular cutout, in which case it'll be a drop in replacement for the speakons. Alternatively just stick with XLR, as they are good for over 10 amps so should see you fine.
 
If the ROE caps aren't cracked in the cases they usually sound and measure fine. Replacing 40+ in a krell ksp7b pre yielded no change.
 
44 in total across 4 boards, so not a small job, allowing for disassembly too. But got to find ways of filling out time while locked in. The XLR are a bit bigger than the now std size, so will need to drill new holes, I may leave them well alone. But have ordered the speakon sockets, so have the option.

@Arkless, I plan to use for bass and sub bass duties, using a Roger sanders ELS amp for ELS panels. So hopefully will be ok
 
if it is a keeper, I will want to replace the front, very ugly steel panel with (ideally) a solid black aluminium 8-10mm panel. Anyone know of a good supplier, UK who can cut to size (I can drill the holes), with rounded corners and able to brush and anodised?

Finding someone who can do the finishing and supply the base plate seems to be hard? Or I may go Black perspex, or bright Aluminium and paint, but would prefer black anodised Aluminium.
 
just made up one speaker cable with xlr plug, so now can test....might wait until 2021, will check DC first, then speakers I can afford to fry!
 
davidismynaim said:
if it is a keeper, I will want to replace the front, very ugly steel panel with (ideally) a solid black aluminium 8-10mm panel. Anyone know of a good supplier, UK who can cut to size (I can drill the holes), with rounded corners and able to brush and anodised?

Finding someone who can do the finishing and supply the base plate seems to be hard? Or I may go Black perspex, or bright Aluminium and paint, but would prefer black anodised Aluminium.
Click to expand...
I have a black 10mm full width 4U aluminum faceplate from Modushop that you could have for the cost of shipping. The only problem is I'm in Spain. It's got a 8mm (IIRC) hole drilled for a toggle switch. It could be drilled out more for a larger switch if you needed (e.g. high current DPST rocker).

I can measure it tomorrow if it's interesting to you.
 
booja30 said:
I have a black 10mm full width 4U aluminum faceplate from Modushop that you could have for the cost of shipping. The only problem is I'm in Spain. It's got a 8mm (IIRC) hole drilled for a toggle switch. It could be drilled out more for a larger switch if you needed (e.g. high current DPST rocker).

I can measure it tomorrow if it's interesting to you.
Click to expand...
Wow. That would be amazing. Do let me know the size. Sounds like it might be close to perfect. That’s very kind of you. Happy new year!!
 
davidismynaim said:
Wow. That would be amazing. Do let me know the size. Sounds like it might be close to perfect. That’s very kind of you. Happy new year!!
Click to expand...

The faceplate is 450mm x 180mm x 10mm, 2.2kg.

It has a 10mm hole centered horizontally, and the hole center is 29mm from the bottom edge. I have a 3D printed bushing in the hole that makes it roughly 6.5mm so that the toggle switch I was using will fit nicely. I can include a NKK 3A DPDT or SPDT switch with black trim washer (in the photo). But you probably need a higher rated switch, and in that case I can enlarge the hole to fit a round push button or a heavy duty rocker switch. I probably have some options here that I don't need.

Let me know if that works, and we can see how cheaply we can get it from me to you.

50786471086_863a5e6ed9_c.jpg

50786471131_18a8819dc2_c.jpg
 
booja30 said:
The faceplate is 450mm x 180mm x 10mm, 2.2kg.

It has a 10mm hole centered horizontally, and the hole center is 29mm from the bottom edge. I have a 3D printed bushing in the hole that makes it roughly 6.5mm so that the toggle switch I was using will fit nicely. I can include a NKK 3A DPDT or SPDT switch with black trim washer (in the photo). But you probably need a higher rated switch, and in that case I can enlarge the hole to fit a round push button or a heavy duty rocker switch. I probably have some options here that I don't need.

Let me know if that works, and we can see how cheaply we can get it from me to you.

50786471086_863a5e6ed9_c.jpg

50786471131_18a8819dc2_c.jpg
Click to expand...

That's amazing!! Perfect size too. I think the best option for the hole is to fit a LED in there as the main on/off is already there at the back. so any reduction collar to help reduce for me to fashion a LED in there would be work me thinks. This is super kind of you. Let me know what the costs are and I can paypal them to you, let me know if you want pounds or euros. I will PM you with my address. How come this is spare?
 
davidismynaim said:
That's amazing!! Perfect size too. I think the best option for the hole is to fit a LED in there as the main on/off is already there at the back. so any reduction collar to help reduce for me to fashion a LED in there would be work me thinks. This is super kind of you. Let me know what the costs are and I can paypal them to you, let me know if you want pounds or euros. I will PM you with my address. How come this is spare?
Click to expand...
When I built my FirstWatt F5 amp I got a stock chassis from ModuShop and drilled the hole myself when I added the switch. I did a 10mm hole to try out a pushbutton option, but found I liked the toggle switch better, so I made the bushing for the threaded rocker switch.

Later on I started a preamp project and decided to have it CNC'd since I was more familiar with CAD by that point. At the same time I ordered a new faceplate for the F5, and had similar machining done to it. It was cheaper to order a new one (since I was already paying shipping for the other chassis) than to send mine back to Modushop (Italy) for them to work on.

50446011142_7386be7a48_c.jpg
 
Ok, finally felt brave enough to try with a speaker I would afford to fry...not good.

Nothing on any of the 4 channels...hmmm, this isn't going to be straightforward.

Looks like replace caps, and figure out what might be causing this fault conditions.

I am now out of depth, so anyone interested at looking at this in the UK, as a chargeable repair project.

Will be contacting seller too, who sold it as working!
 
If you have 4 channels which appear not to work yet the DC offset is O.K. I wouldn`t go random cap changing until the actual fault is found. You`re likely to cause more faults than you fix.
 
Could it be anything to do with the Split/Bridge switch at the input ?, try moving a few times it could have dirty contacts
Alan
 
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