I would try that first.
Is it a home made pcb or manufactured ?
Quite a bit has to right to get a good joint. Right solder, soldering tip good, soldering hot enough etc etc.
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Manufactured, bought on Fleabay, made in China of course. I never used to have trouble back in the day and a bit of a play this evening with some old veroboard and an old PCB from a scrap amp suggests nothing wrng there. Maybe the new PCB is just greasy. The solder just seems to want to stay on the cmponent leg and not flow into the joint.
More than likely, following things could be the reasOns for bad sOlder joints.
1. Solder wire being bad and old having lost its flux properties,- solution is to get a new wire, 0.8mm
2. Pcb having large tracts of planes with no thermaL relief. SOlution is heat the pad fIrst and then the lead and then introduce soLder. Some judgement is required so as not to over heat anything.
Typing from a mobile with ungainly keypad. Sorry for mistakes.
Regards
Prasi
1. Solder wire being bad and old having lost its flux properties,- solution is to get a new wire, 0.8mm
2. Pcb having large tracts of planes with no thermaL relief. SOlution is heat the pad fIrst and then the lead and then introduce soLder. Some judgement is required so as not to over heat anything.
Typing from a mobile with ungainly keypad. Sorry for mistakes.
Regards
Prasi
I'd say that if you build it with a lower voltage because that's what you've got then it will work, albeit with very low power. It's certainly enough to get it running and decide whether you like it. This may be enough for what you want, maybe you only have a small room, efficient speakers and so on. If it's not then changing to a bigger supply voltage isn't complicated.
Hmm...8V or so rails are a bit low for use with hifi speakers, at least. I had a '96 version based on a 9V+9VAC transformer for a few years. It was paired with typical 160mm, 87 dB sensitivity bookshelf speakers but it just didn't do quite enough with bass before clipping. My reference was a standard 33VDC supply JLH'69 which had more headroom.
The comparison was done using smaller speakers since many of us would presume from a retail point of view, that they would be a suitable match but this doesn't really work. You probably need more power or rather headroom, than you think or you may need to add a powered subwoofer, all depending on the speakers and the listening area, of course.
The comparison was done using smaller speakers since many of us would presume from a retail point of view, that they would be a suitable match but this doesn't really work. You probably need more power or rather headroom, than you think or you may need to add a powered subwoofer, all depending on the speakers and the listening area, of course.
A possible workaround could be to use Schottkys here (fe SB540/SB550). This way you could possibly get into the +/-9V territory at 2x 7.1V AC.
The thig with smaller speakers is that most likely you will have to use some sort of a bass-lift which will naturally eat into amp's available headroom.
Hooray! Thanks for the advice to give it a scrub with some abrasive paper, a bit of a rub has sorted it, I was being too delicate. 600 grit glasspaper has the solder flowing nicely.
A bit more thinking - I am measuring up for the heat sink. All OK, but what is the protocol for insulating the board from the bracketry and heat sink? I have bought some mica insulators, got the wrong ones, TO3P not TO3, so that's an error. i will buy some TO3 kits. The thing has 3 x 2N3055 per channel, 2 setting up the voltage divider for the output, one on rthe PSU capacitor multiplier. I am attaching it to a 3mm ally angle attached to a heatsink. Am I right in thinking that I need (as seen from above) the trannies sitting on a mica pad, with thermal grease, then the ally bracket, then another mica pad, then the PCB (which has copper on the top surface so needs insulating with the second mica pad) then the thing held together with M4/M3 nuts and bolts, a star washer where the nut meets the PCB to pick up the collector, and sleeves on the 2 legs and 2 bolts to keep the electrical connectors away from the bracket? Is this best practice?
A bit more thinking - I am measuring up for the heat sink. All OK, but what is the protocol for insulating the board from the bracketry and heat sink? I have bought some mica insulators, got the wrong ones, TO3P not TO3, so that's an error. i will buy some TO3 kits. The thing has 3 x 2N3055 per channel, 2 setting up the voltage divider for the output, one on rthe PSU capacitor multiplier. I am attaching it to a 3mm ally angle attached to a heatsink. Am I right in thinking that I need (as seen from above) the trannies sitting on a mica pad, with thermal grease, then the ally bracket, then another mica pad, then the PCB (which has copper on the top surface so needs insulating with the second mica pad) then the thing held together with M4/M3 nuts and bolts, a star washer where the nut meets the PCB to pick up the collector, and sleeves on the 2 legs and 2 bolts to keep the electrical connectors away from the bracket? Is this best practice?
You really need to cover the whole of the underneath of the angle with an insulating material. As you tighten up the bolts it will bend down on to the top copper tracks.
It really should have no tracks on the top and no vias under the angle either.
It really should have no tracks on the top and no vias under the angle either.
An externally hosted image should be here but it was not working when we last tested it.
I don't know which PCB you are using (sorry, not read all this part of the thread), but I'm surprised if two sided PCB's use copper on both sides of the board around the TO-3 cans as there is plenty of room to get a track or two in, which would allow you to bolt the ally direct onto the (top) of the PCB (without tracks). I've used M3 nylon washers with shoulders which are normally used to insulate the screws by cutting the shoulders off to leave an insulating cylinder.
If there is copper on the top side of the PCB then it is usual as Nigel points out to get a complete insulating strip (you can buy sheets or strips) and cover the whole PCB surface.
Normally I use plain washers to connect the screw to the PCB and the star washer next between the plain and the nut - the standard arrangement for locking washers. I do this on the principle that the plain washer will make the largest contact area to the track and is more conductive than the steel star washer. Whereas a star washer is very likely to cut into the copper tracks.
If there is copper on the top side of the PCB then it is usual as Nigel points out to get a complete insulating strip (you can buy sheets or strips) and cover the whole PCB surface.
Normally I use plain washers to connect the screw to the PCB and the star washer next between the plain and the nut - the standard arrangement for locking washers. I do this on the principle that the plain washer will make the largest contact area to the track and is more conductive than the steel star washer. Whereas a star washer is very likely to cut into the copper tracks.
Thanks gents,
I'm using a PCB from Ebay, made in China of course, and double sided. It has tracks buried inside it and the important stuff (PSU in, audio out, smoothing caps) are on big heavy copper tracks. The holes have copper inside. Thinking about it, as you say Nigel I will need electrical and thermal insulation between the ally bracket and the PCB, I don't want the PCB warming up and the heat will be on the trannies on the heat sink, the PCB won't (shouldn't) be generating any significant heat. With that in mind will a couple of thicknesses of PVC tape do that, or do I need to buy something? For the legs passing through the ally I can add a bit of heat shrink.
Star nuts facing the nut too, not the board. Didn't think it went that way round, so thank you. On cars it's often the other way (istr) because they suffer from corrosion and getting a star washer well chewed into the casting is generally a winner for electrical continuity.
I'm using a PCB from Ebay, made in China of course, and double sided. It has tracks buried inside it and the important stuff (PSU in, audio out, smoothing caps) are on big heavy copper tracks. The holes have copper inside. Thinking about it, as you say Nigel I will need electrical and thermal insulation between the ally bracket and the PCB, I don't want the PCB warming up and the heat will be on the trannies on the heat sink, the PCB won't (shouldn't) be generating any significant heat. With that in mind will a couple of thicknesses of PVC tape do that, or do I need to buy something? For the legs passing through the ally I can add a bit of heat shrink.
Star nuts facing the nut too, not the board. Didn't think it went that way round, so thank you. On cars it's often the other way (istr) because they suffer from corrosion and getting a star washer well chewed into the casting is generally a winner for electrical continuity.
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Greetings to all,
I would like to ask all those who have been able or wanted to replace in the JLH amplifier the original final transistors (2N3055) with other types such as results obtained in sonic terms, such as changes or characterizations found between one device and another.
In particular, currently my amp mounts mj15003 and I would like to replace them with mj21194 in hopes of improving, but I would like to know if there will be improvements and if there will be of what nature and sonic entity, if the replacement is worth it .
I thank everyone in advance who wants to expose their experience.
HI!
Mleod
I would like to ask all those who have been able or wanted to replace in the JLH amplifier the original final transistors (2N3055) with other types such as results obtained in sonic terms, such as changes or characterizations found between one device and another.
In particular, currently my amp mounts mj15003 and I would like to replace them with mj21194 in hopes of improving, but I would like to know if there will be improvements and if there will be of what nature and sonic entity, if the replacement is worth it .
I thank everyone in advance who wants to expose their experience.
HI!
Mleod
Another transistor question, the 1969 design I have specifies 2 off D667 transistors per channel. One is in the capacitor multiplier as the upper half of the darlington pair, the other is the upper transistor in the darlington pair formed with the lower of the 2 power transistors. I only bought 2, didn't realise that this is per channel. I measured the gain on each, they are 180. The spec says hFE min 60 max 320 so hardly a precision item. I have 2 x NPN transistors in the bits box, gain measured at 180-200, no ID code visible. They are in a metal can with tag by emitter, like the good old BC107/109 were. Can I substitute these for D667?