Hart JLH find....please help with identity/info!!

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These are the boards that I have .... and still make

James, as I mentioned earlier, this Hart kit was my first foaray into DIY Audio and I remember the amp with affection. I recall I was very impressed with the sound quaity I achieved with it.

It looks as though you make the boards the old-fashioned way - I guess you only have a film image of the PCBs? I wonder if it is worth the effort to put the design into a PCB CAD package to generate gerber files for modern board fabrication? Maybe adapt/update it for some current parts too?

Ray
 
hello thanks for the link .. great info

You're welcome.

I still use Terry (Canterbury) for custom toroids, but his order book always seems to be pretty full and I've found Toroidy to be an excellent supplier for more 'standard' requirements on a shorter lead time; their quality is excellent, much better than the items offered by Farnell, RS, et al.
 
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It's morning...and sorry James for having t 'give in' last night...but thanks for the contributions!
Thanks also Ray for the Polish link.....coming in around £65 (ish)


Need to be sure that existing Transformer is Kaput before investing that heavily tho'... :)


Story: On re-assembling both amps...side by side...following extensive cleaning (it had to be done!) amp in question powered up (green led), crinkling noise from wrapping...and a few seconds later, popped a 13A fuse at the wall. (Aaagghh...should've been a 3A..??)


Minutes later....transformer was now HOT!!


On cooling, I have checked windings for continuity...all good...nothing leaking between primary/2ndary...so good??


Occurs that this transformer...perhaps...is not the original supplied with kit....it has a different style of 'crimped on connectors'....different from the rest. Same physical size tho'...
Will be taking a good look at this today for any identifying marks.


To be fair...picked up the pair without demo...in a filthy state...and so problems perhaps to be expected!
 
It would work; it's similar quality to that sold by Farnell & RS. It's a good amp, worth getting quality parts for IMO.

Have you determined that it's the transformer that needs replacing; a transformer will get hot if you ask it to deliver more current than it's rated for so there may be something else that's the underlying problem. I think you need to do some trouble-shooting before shelling out for parts you don't actually know you need.

You might want to consider installing a fuse for the transformer, rated for it's load, rather than relying on the mains plug fuse.
 
It would work; it's similar quality to that sold by Farnell & RS. It's a good amp, worth getting quality parts for IMO.

Have you determined that it's the transformer that needs replacing; a transformer will get hot if you ask it to deliver more current than it's rated for so there may be something else that's the underlying problem.

You might want to consider installing a fuse for the transformer, rated for it's load, rather than relying on the mains plug fuse.


Must admit...tend to agree about getting quality bits!!
Still to determine if Trans. is OK...Continuity looks OK FWIW.
Would measuring resistances of windings help???
 
You might want to consider installing a fuse for the transformer, rated for it's load, rather than relying on the mains plug fuse.


I would say that's best practice with transformers. Internal fuse to protect the primary - using an externally accessive fuse is asking for some clown swapping in the wrong value at some future point, no matter how big the legend saying "only use correctly rated fuse". The fuse in the plug is to protect the flex from starting a fire.
 
I would say that's best practice with transformers. Internal fuse to protect the primary - using an externally accessive fuse is asking for some clown swapping in the wrong value at some future point, no matter how big the legend saying "only use correctly rated fuse". The fuse in the plug is to protect the flex from starting a fire.


Sounds like a plan...will be doing this as a matter of course...with appropriate guidance!!
 
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Hello .. in this model of build the sec are not fused, you could have a shorted bridge rec diode, does happen. unplug the sec connections from the main psu board, if the fuse still blows pretty much 100% faulty transformer .. my bet is the fuse will not blow with the sec connections disconnected unless the transformer is already damaged. When I make my amps I always fuse the sec winding
 
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