Hi, All,
Over twenty years ago, i built a JlH 1969 for my son using a couple of Heart Kits. For a cabinet I used a scrap Pub rack mounted amp box...
This amplifier is still going strong today.
Recently, I decided to build one for myself and bought a couple of chinese copies to speed things up. I fitted MJ15003's rather than the obviously old - used - 3055's.
The heatsinks are 4x RS Black 6x5".
The new build has worked fine for one night then today the left channel went distorted, getting worse and Q1 was boiling hot and Q2 very cool.
Q2's collector is at 2.5v and I cannot reset mid point voltage.
Current drain is still 1 amp as set by me initially...
Any help will be appreciated.
Kind Regards,
Michael
Over twenty years ago, i built a JlH 1969 for my son using a couple of Heart Kits. For a cabinet I used a scrap Pub rack mounted amp box...
This amplifier is still going strong today.
Recently, I decided to build one for myself and bought a couple of chinese copies to speed things up. I fitted MJ15003's rather than the obviously old - used - 3055's.
The heatsinks are 4x RS Black 6x5".
The new build has worked fine for one night then today the left channel went distorted, getting worse and Q1 was boiling hot and Q2 very cool.
Q2's collector is at 2.5v and I cannot reset mid point voltage.
Current drain is still 1 amp as set by me initially...
Any help will be appreciated.
Kind Regards,
Michael
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Are the transistors original or the ones that came with the kit? Because there is something that comes with the kit - most likely fake.
Thanks for the replies above.
Re the above post, the problem is solved. I had a dry joint on the base of Q4.
I decided to change Q4 because the voltages were wrong round it.
then, as I cut the collector leg I noticed that the base leg was moving. The soldering on the underside looked normal so i re-soldered the collector leg and the base leg and everything fired up nicely.
Kind regards,
Michael.
Re the above post, the problem is solved. I had a dry joint on the base of Q4.
I decided to change Q4 because the voltages were wrong round it.
then, as I cut the collector leg I noticed that the base leg was moving. The soldering on the underside looked normal so i re-soldered the collector leg and the base leg and everything fired up nicely.
Kind regards,
Michael.
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Sorry, Osscar.
The Original 3055's looked old and dirty with signs of solder on the legs.
I had already purchased four 15003's from RS in anticipation of that.
My son is so impressed with my cabinet (not my strongest skill usually) that I might take the china pcb's and build originals on perf board.
Michael
The Original 3055's looked old and dirty with signs of solder on the legs.
I had already purchased four 15003's from RS in anticipation of that.
My son is so impressed with my cabinet (not my strongest skill usually) that I might take the china pcb's and build originals on perf board.
Michael
Unless it's purely a nostalgia thing, I wouldn't revert to Perfboard or matrix board etc. where the risk of errors, poor layout and solder joints is significant. You can usually buy several types of JLH'69 and other, later version PCBs quite cheaply, sometimes from the same sources as the kits.
With their printed parts overlays and generally, better integrity and performance when assembled, you also have a permanent, inbuilt parts identifier for times when all those useful details have been forgotten and lost. 'Worth a bit of consideration, at least.
With their printed parts overlays and generally, better integrity and performance when assembled, you also have a permanent, inbuilt parts identifier for times when all those useful details have been forgotten and lost. 'Worth a bit of consideration, at least.
Ian,
What you say is true but I just feel that it would be good to hear the original.
Also, the supplied pcb's do not lend themselves to easy swap-outs.
Especially with my aged hands, eyes and ears.
I build these days because I cannot let go of the excitement of first switch-on...
Funny, isn't it that we can buy a complete and boxed JLH from china for less than the price of the heatsinks from RS but the listening pleasure is much greater from one's own build.
I don't post very often but I refer to this site often.
Michael
What you say is true but I just feel that it would be good to hear the original.
Also, the supplied pcb's do not lend themselves to easy swap-outs.
Especially with my aged hands, eyes and ears.
I build these days because I cannot let go of the excitement of first switch-on...
Funny, isn't it that we can buy a complete and boxed JLH from china for less than the price of the heatsinks from RS but the listening pleasure is much greater from one's own build.
I don't post very often but I refer to this site often.
Michael