Hi! Brand new to this forum. All those on this site sound like they know their stuff....I am unfortunately just someone who listens to a lot of music and loves the sound of this Leak stereo 70. Stupidly whilst messing with it, a couple of components fried. I have now been listening with a cheap car amplifier linked to my Missions. Not very happy🙁
I am no expert...I can handle a soldering iron and even know which components I need.err...by pointing. But as far as to values and voltages I am lost.
I need to locate 4 components...2x 64uf- 64 v capacitors 2x resistors.
Surely this can't be so hard? The items are on the amp board.
Can anyone help me locate items or find modern replacements?
I have tried reading the schemetic diagram, but unfortunately never learned Greek.
Any help gratefully received. Please don't leave me to the sound of this car amp!
Hopefully pic of board below...
I am no expert...I can handle a soldering iron and even know which components I need.err...by pointing. But as far as to values and voltages I am lost.
I need to locate 4 components...2x 64uf- 64 v capacitors 2x resistors.
Surely this can't be so hard? The items are on the amp board.
Can anyone help me locate items or find modern replacements?
I have tried reading the schemetic diagram, but unfortunately never learned Greek.
Any help gratefully received. Please don't leave me to the sound of this car amp!
Hopefully pic of board below...
Can you post a better photo, from above the pcb please? Showing the value of the other green wire wound resistor?
I would replace;
P5 220R preset
R52 1R0 2.5Watt Wire Wound
R50 10R 10% (or better) 1/2 Watt
T8 2N2102
T9 2N4036
and the output 2N3055 transistors then see what happens setting the quiescent current on the link to 30 - 35mA.
P5 220R preset
R52 1R0 2.5Watt Wire Wound
R50 10R 10% (or better) 1/2 Watt
T8 2N2102
T9 2N4036
and the output 2N3055 transistors then see what happens setting the quiescent current on the link to 30 - 35mA.
Great amps, I used to love mine - however, it's VERY, VERY unlikely that it only needs the resistors. The two green resistors are the 1 ohm output emitter resistors, and are almost certainly fried because the output transistors are S/C - plus there could also be other transistors damaged.
The circuit is here:
http://44bx.com/leak/Leak/Circuits/cctStereo70.gif
The circuit is here:
http://44bx.com/leak/Leak/Circuits/cctStereo70.gif
Wow that was quick! Seriously impressed!
One of the green wire wound resistors is just now de soldered and has written on it 1 ohm 20 %.
Your second reply is just gobbledegook to me. Did I mention I wasn't any good at this?
One of the green wire wound resistors is just now de soldered and has written on it 1 ohm 20 %.
Your second reply is just gobbledegook to me. Did I mention I wasn't any good at this?
See this thread http://www.diyaudio.com/forums/solid-state/96964-leak-stereo-70-fault.html
There are better threads here that actually show the PCB layout and schematic diagram, but bing is too busy trying to sell me PCB layout software for the windows I don't own, to give them to me. Perhaps you could type inthe search "leak stereo 70 pcb layout" and page through several pages to look at other diyaudio results.
Those appear to be the 1 ohm 5 watt? resistors, and C32 and C29, which are 64 uf (formerly mf) capacitors at 34 and 43 volt nominal load. Perhaps you should buy a couple of 68 uf 80 v capacitors, since those will be available. I would replace every other electrolytic capacitor in the device, those things are beer cans sealed with cheap rubber, and the rubber turns to dirt in 25 years or more. I like to buy the long life variety rated >3000 hours service life, rather than the on the shelf store grade which lasted about 4 years before wimping out in my Dynakit ST70.
If the emitter resistors are blown, it is likely the output transistors are, and usually the driver transistors and some other things. You need to learn to make the diode check with the ohms 2000 scale or diode scale of a dvm; there are 4 checks of a transistor - be forwards (~600) bc forwards (same) be backwards (1999) and bc backwards (same) . Farnell.com and digikey.com put the hours service life in the selector table, other vendors make you download the datasheet and read it or don't tell you brand, grade, or anythings else useful. RS is a big UK supplier, I haven't used their website. You'll want to convert to radial lead caps, those are a lot longer life than the axial lead caps still available.
For replacements the MJ15015 output transistors are slightly tougher than the old 5 digit RCA transistors (TO3) and for driver transistors TIP41C and 42C are nice and available, but the pinout is different and you have to twist the leads around. You can buy TO220 heatsinks, but I tend to saw up a bit of aluminum window molding and put a hole in it for these low wattage drivers. You will need a little heat sink compound - wash up after use, it is poisonous. If you want a bit wimpier driver with a more similar pinout, try BD139/140. You can get the datasheets on datasheetcatalog.com.
Good luck, I'm running my 1971 build ST120 into the 43 year after a rebuild and a little upgrading. IMHO that amp is a copy of the Leak, or vice versa, who can tell. 10 ohm 1 W resistors between the driver card and the bases of the output transistors are recommended since the factory that built those old homotaxial output transistors has been redeveloped as a parking lot, and 47 pf disk caps between b and c of the drivers might retroactively reduce the chance of ultrasonic oscillations since the new output transistors are so much faster than the old. I just tacked these on the bottom of the card on the ST120, which is probably a copy of the Leak design. See the greg dunn website on the ST120 for more details of the "TIP mod" where dynaco coped with the faster 2n3442 output transistor only 9 years after the original card design for the 5 digit ones selected for higher Vceo from the 2n3055 production stream.
There are better threads here that actually show the PCB layout and schematic diagram, but bing is too busy trying to sell me PCB layout software for the windows I don't own, to give them to me. Perhaps you could type inthe search "leak stereo 70 pcb layout" and page through several pages to look at other diyaudio results.
Those appear to be the 1 ohm 5 watt? resistors, and C32 and C29, which are 64 uf (formerly mf) capacitors at 34 and 43 volt nominal load. Perhaps you should buy a couple of 68 uf 80 v capacitors, since those will be available. I would replace every other electrolytic capacitor in the device, those things are beer cans sealed with cheap rubber, and the rubber turns to dirt in 25 years or more. I like to buy the long life variety rated >3000 hours service life, rather than the on the shelf store grade which lasted about 4 years before wimping out in my Dynakit ST70.
If the emitter resistors are blown, it is likely the output transistors are, and usually the driver transistors and some other things. You need to learn to make the diode check with the ohms 2000 scale or diode scale of a dvm; there are 4 checks of a transistor - be forwards (~600) bc forwards (same) be backwards (1999) and bc backwards (same) . Farnell.com and digikey.com put the hours service life in the selector table, other vendors make you download the datasheet and read it or don't tell you brand, grade, or anythings else useful. RS is a big UK supplier, I haven't used their website. You'll want to convert to radial lead caps, those are a lot longer life than the axial lead caps still available.
For replacements the MJ15015 output transistors are slightly tougher than the old 5 digit RCA transistors (TO3) and for driver transistors TIP41C and 42C are nice and available, but the pinout is different and you have to twist the leads around. You can buy TO220 heatsinks, but I tend to saw up a bit of aluminum window molding and put a hole in it for these low wattage drivers. You will need a little heat sink compound - wash up after use, it is poisonous. If you want a bit wimpier driver with a more similar pinout, try BD139/140. You can get the datasheets on datasheetcatalog.com.
Good luck, I'm running my 1971 build ST120 into the 43 year after a rebuild and a little upgrading. IMHO that amp is a copy of the Leak, or vice versa, who can tell. 10 ohm 1 W resistors between the driver card and the bases of the output transistors are recommended since the factory that built those old homotaxial output transistors has been redeveloped as a parking lot, and 47 pf disk caps between b and c of the drivers might retroactively reduce the chance of ultrasonic oscillations since the new output transistors are so much faster than the old. I just tacked these on the bottom of the card on the ST120, which is probably a copy of the Leak design. See the greg dunn website on the ST120 for more details of the "TIP mod" where dynaco coped with the faster 2n3442 output transistor only 9 years after the original card design for the 5 digit ones selected for higher Vceo from the 2n3055 production stream.
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BTW check your speakers are over 6.5 ohm with the meter, old amps blow up for a reason. The crossover e-caps to the tweeter could have shorted, or the rubber surround on the woofer deteriorated causing the windings to scrape , rub the insulation off, and cause a shorted turn. You push the woofer center in and out with your finger gently to check the suspension- it should be nice and smooth, no bumpy scraping. Foam surround is the worst. You can't measure a shorted turn really, if you feel scraping you need to replace the driver. e-caps, well you see what I and the guy on the other thread think about old ones. e-caps in the speaker will be non-polar electrolytics, with a "NP" after the voltage. Those are hard to buy, in the US Partsexpress.com specializes in speaker parts. mcmelectronics.com has a non-polar caps, that is another US outlet of farnell.com, the one that specializes in consumer and PA equipment. When electronic ordering, minimizing freight is a goal, that tends to cost more than the parts typically, so I try to get everything in as few orders as possible, whether I need the actual $.38 part or not. The freight charge minimum is $7 from farnell, or $12 from mcmeletronics . More (via UPS or Fed-Ex ground) if your address is not a business address. I used to buy parts from a physical store, but they stocked only absolute **** grade parts, or out and out rejects. The NTE semiconductors in the stores were okay quality, but they cost ten times what industrial number parts cost from Allied radio mail order, farnell (newark in the US) etc. Reliable semiconductor houses are On Semi, TI (national/fairchild) ST, maybe Vishay but nobody sells them here so I don't know. Central Semi sells a lot of "exact copy" parts with half the specifications left off the datasheet, because they don't test for that. I tend to stay away from them. A-grade cap manufacturers are Nichicon, Rubicon, Panasonic, Vishay Sprague. All sell 500 hour parts for the rot-gut market, READ the life specification on what you cap you buy if you're not going to dump the system on somebody else. For those resistors, buy flameproof wirewound, pennies more and worth it. Vishay again.
Be afraid of E-bay, the caps may be past life, the semiconductors may be fakes upgraded with paint to something more expensive. Farnell sells out of shelf life e-caps with an asterisk at a discount, those you need to charge up with the DVM ohms scale to "reform" them before installing. Observe polarity, backward voltage on an e-cap makes them blow the tops and leak. When buying stuff, get new mica washers for the TO3 transistors, those age badly too. Farnell has a nice little kit with new plastic ferrules too in the same bag.
Don't forget 3 mm screw hardware for the heatsinks and the new transistors. The holes in the MJ15015 will be smaller than the old #6 machine screw holes in the 2n3055. Buy washers too, 4mm might fit better but it might not, with washers you only need one size. I used 4-40 hardware in the US, but that is not a British spec.
Be afraid of E-bay, the caps may be past life, the semiconductors may be fakes upgraded with paint to something more expensive. Farnell sells out of shelf life e-caps with an asterisk at a discount, those you need to charge up with the DVM ohms scale to "reform" them before installing. Observe polarity, backward voltage on an e-cap makes them blow the tops and leak. When buying stuff, get new mica washers for the TO3 transistors, those age badly too. Farnell has a nice little kit with new plastic ferrules too in the same bag.
Don't forget 3 mm screw hardware for the heatsinks and the new transistors. The holes in the MJ15015 will be smaller than the old #6 machine screw holes in the 2n3055. Buy washers too, 4mm might fit better but it might not, with washers you only need one size. I used 4-40 hardware in the US, but that is not a British spec.
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