Ahhh... the plot thickens. The resistor is indeed 10R, which fits with R18. Yet it's in R17s position. (Note the shadows of the traces on the bottom of the board, highlighted in yellow in the attached image.)
Note also that Soundhappy's middle picture does indeed have both a R17 and a R18.
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Yes I know. Maybe I could improvise some.Your amp chassis doesn't have any through holes for air flow.
Source resistors are hot and probably more and more in closed box.....
Greetings
Temperature stabilisation is very important factor for class A amplifier.
This takes some time normaly ~ 1hour.
With this very closed chassis they go hotter and hotter
so temperature is hard to stabilise and disaster can happen.
Hello,
My friend got back his Hiraga. The output was reduced but that isnt a problem for him but the sound was surely improved!!
He still uses the original caps. I think that 2 decades ago the quality of parts like caps was better. There were severaql brands that made real good parts. Now only a few left.
The Shinkoh resistors are way better than the ones used in most present Hiraga amps.
They dont use the original transistors so in fact they are not Hiragas.
The Hiraga needs proper cooling.
Me and my friend both used chokes in the power supply.
The 1K8 and the 0,47 ohm can both be improved.
Greetings, Eduard
Hello,
Tell your technician to use some kind of stand off to raise the heatsinks around15/20 mm or so.
Resolder? Maybe he should just cut and inch or so and make a '' fresh '' solderjoint.
Today someone at my company did check the complete electricity contact material with a Fluke temperature meter. There were some bad ones resulting in excessive heating.
Your amp probably needs a serious inspection. The 0,47 ohm and the resistors in the power supply are probably heating up parts in their surroundings.
Probably the people who build your amp did try to improve it but the execution is done in such a way that you end up with one not even close to the original Hiraga.
Greetings, Eduard
Tell your technician to use some kind of stand off to raise the heatsinks around15/20 mm or so.
Resolder? Maybe he should just cut and inch or so and make a '' fresh '' solderjoint.
Today someone at my company did check the complete electricity contact material with a Fluke temperature meter. There were some bad ones resulting in excessive heating.
Your amp probably needs a serious inspection. The 0,47 ohm and the resistors in the power supply are probably heating up parts in their surroundings.
Probably the people who build your amp did try to improve it but the execution is done in such a way that you end up with one not even close to the original Hiraga.
Greetings, Eduard
Look great YES !
....well components on the pcb's need air flow
specially source power resistors run very hot inside of very closed chassis box.
After few hours they cook inside....
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Look great YES !
....well components on the pcb's need air flow
specially source power resistors run very hot inside of very closed chassis box.
After few hours they cook inside....
There are no signs of overheating on the PCBs*. Cooking is good for Class A!
Cheers,
Jeff.
* Most of the ageing appears to be from a failure to clean off the flux residue on the solder joints.
There are no signs of overheating on the PCBs*. Cooking is good for Class A!
Cheers,
Jeff.
Hello,
You should read the original articles written by Jean Hiraga.He writes a lot on getting rid of the heat. Soundhappy is French and i can read French so we both did.
Greetings, Eduard
Yeah, that wouldn't worry me (marble can take a LOT of heat). But I do recognise that others might have different tolerances for this sort of thing.
Cheers,
Jeff.
There are no signs of overheating on the PCBs*. Cooking is good for Class A!
Cheers,
Jeff.
* Most of the ageing appears to be from a failure to clean off the flux residue on the solder joints.
I guess this guy don't bias them in class A or was not use this amplifier for long session in the summer season.
Put 4 power resistors with high bias for 7 hours in such "box" chassais and things can go seriously problematic.
I have original Hiraga 20 watts version in my home and yeah 0.47R is going very hot but my have lot of air around so all is safe.
Btw i change for bigger wattage source resistors and they are on the open air side not in close box. Normaly you need all voltage's and current's from the schematic values match your Hiraga amp so all OK at this point.
I never see pure class A amplifier circuit in closed boxes why ?
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Hello, Then one day you come and you see this. The appartment is mine after a repair on the little roof with tar and a heater the '' spiderweb? '' in the dilation caught fire after the professionals left. House was filled with smoke, they rang my bell, nobody answered so they forced their way inside to check if nobody is there.
In my Thai hotel they have done the same . Only there the firebrigade took my camera gear on their way back home.
So please dont heat up things to much.
Greetings, Eduard
In my Thai hotel they have done the same . Only there the firebrigade took my camera gear on their way back home.
So please dont heat up things to much.
Greetings, Eduard
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Yes i see braun colour and with all the wood around that is not safe and hard to temperature stabilise that is very important
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I can fix the internal heating problem - my priority is getting it working right so I can feel safe connecting my Tannoys: lolYes i see braun colour and with all the wood around that is not safe and hard to temperature stabilise that is very important
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