Hi Everyone,
I have a Leak 2000 which has a blown output transistor, however after searching the net, I cannot find which type of transistor this is. It looks like a Motorola 441, but all searches have drawn a blank.
Does anybody know what the full Motorola part number it, or is there a replacement that most people use in this application.
I mentioned the Leak 2200 as the circuit looks identical
Any help greatly appreciated
Many thanks
Martin
I have a Leak 2000 which has a blown output transistor, however after searching the net, I cannot find which type of transistor this is. It looks like a Motorola 441, but all searches have drawn a blank.
Does anybody know what the full Motorola part number it, or is there a replacement that most people use in this application.
I mentioned the Leak 2200 as the circuit looks identical
Any help greatly appreciated
Many thanks
Martin
I've not heard of that one, and its not listed in an ancient 'Towers' selector either.
If you need replacements then we would need to see the circuit details, or at the very least know what supply voltages are used, the package outline (guessing T03) and whether its an NPN or PNP device.
If you need replacements then we would need to see the circuit details, or at the very least know what supply voltages are used, the package outline (guessing T03) and whether its an NPN or PNP device.
TR21 is PNP and TR22 is NPN.
I don't know the can they are in but if T03 I would use 2N3055 and MJ2955 or if different select another from the TIP range.
HT is only 32V + / - so almost anything in the medium current range will suit.
I don't know the can they are in but if T03 I would use 2N3055 and MJ2955 or if different select another from the TIP range.
HT is only 32V + / - so almost anything in the medium current range will suit.
Thank you for the replies
What has thrown me is that they are not TO3 but a large flat pack device, otherwise I would have gone with the 3055/2955 route. Thinking about it, they are available in a flat pack version, so probably worth getting a pair to try.
Many thanks once again for the replies
Best regards
Martin
What has thrown me is that they are not TO3 but a large flat pack device, otherwise I would have gone with the 3055/2955 route. Thinking about it, they are available in a flat pack version, so probably worth getting a pair to try.
Many thanks once again for the replies
Best regards
Martin
Hi Andrew,
It has a pair per channel, four in total. Rated output is 30w per channel into 8 ohm 10 to 40khz + and - 32V power supply
Best regards
Martin
It has a pair per channel, four in total. Rated output is 30w per channel into 8 ohm 10 to 40khz + and - 32V power supply
Best regards
Martin
There's a free download of a reasonable service manual scan here: Download the Leak 2000 manuals for free - Hifi Manuals.
Is it possible that the reference to "441" meant BD441/442 or MJE441/442 drivers may have been fitted in this amp? It's an inverting, CFP design and I'd think it may have been a tad prone to instability, given the extra parts around the output stage.
Is it possible that the reference to "441" meant BD441/442 or MJE441/442 drivers may have been fitted in this amp? It's an inverting, CFP design and I'd think it may have been a tad prone to instability, given the extra parts around the output stage.
Yes, Tip3055 and 2955 will serve admirably.
Don't forget to fix the original fault and check the driver stage!
Don't forget to fix the original fault and check the driver stage!
Thank you very much for the information and suggestions regarding the output transistors. I tried to repair the original faulty channel by a reasoned fault finding, but gave in and replaced all the transistors, lifted all the resistors and capacitors and checked their values - replacing as necessary - and sure enough it worked fine. However how on earth did the second channel (LH) suddenly start taking too much current? I've repaired loads of amps, instrumentation and oscilloscopes and this has really given me the run around!
It's probable that the output stage (Complementary feedback pair type) is only marginally stable. Note the caps around the output stage for that reason. There could well have been oscillation as evidenced by increased quiescent current. Why that would occur when you repaired the other channel isn't clear but I assume you were also changing components that were in common, such as power supply caps.
that tells me that the output devices should have a total power of ~150W
That means any 75W devices should be reliable at this output power.
no problem in using higher power devices, but don't go much lower, certainly no lower than 60W
Hi Ian,
Thank you very much for your reply. I had hoped to just get it up and running and work from there, but its turning into a bit of a mission! Agree about the oscillation theory, I'll do a bit of probing with the scope, but when the current went skyward I turned it off pretty sharp to avoid damage. The power supply caps are the original PYE manufacture and I'll be replacing them and the other electrolytics now as a matter of course.
Its been a challenge!
Best regards
Martin
Thank you very much for your reply. I had hoped to just get it up and running and work from there, but its turning into a bit of a mission! Agree about the oscillation theory, I'll do a bit of probing with the scope, but when the current went skyward I turned it off pretty sharp to avoid damage. The power supply caps are the original PYE manufacture and I'll be replacing them and the other electrolytics now as a matter of course.
Its been a challenge!
Best regards
Martin
When you say the current suddenly went skyward, I also think of thermal instability when Q13 loses control of the bias current and as the output stage warms up, the current does too - uncontrollably!
It may be possible to rectify such a thermal runaway problem by mounting the drivers on their own small heatsink with Q13, as is now the preferred method for CFP designs.
It may be possible to rectify such a thermal runaway problem by mounting the drivers on their own small heatsink with Q13, as is now the preferred method for CFP designs.
Hi Ian,
That sounds very much the sort of issue this amp is having. I wonder how many other 2000's and 2200's have had this sort of an issue. I think that I will change all the electrolytics, including the PSU pair and then give this mod a try. Understand completely the theory behind the mod and it makes real sense.
Thanks once again Ian
Best regards
Martin
That sounds very much the sort of issue this amp is having. I wonder how many other 2000's and 2200's have had this sort of an issue. I think that I will change all the electrolytics, including the PSU pair and then give this mod a try. Understand completely the theory behind the mod and it makes real sense.
Thanks once again Ian
Best regards
Martin
Hi Everyone,
Finally got the Leak 2000 up and running and properly set up. Duff electrolytics, and quiescent current setting pots were the main culprits, plus a really poor repair my someone previously who had used the wrong transistors.
I have to say it sounds really good. I'm especially impressed with the disc input stage.
Thank you for all your helpful comments
Best regards
Martin
Finally got the Leak 2000 up and running and properly set up. Duff electrolytics, and quiescent current setting pots were the main culprits, plus a really poor repair my someone previously who had used the wrong transistors.
I have to say it sounds really good. I'm especially impressed with the disc input stage.
Thank you for all your helpful comments
Best regards
Martin
Leak could not make any money out of their amplifiers.
This may indicate they put too many expensive resources into the builds.
This may indicate they put too many expensive resources into the builds.
Hi Andrew,
The 2000 is built like a battleship inside. God knows what the parts bill would be for it. All those switches, heavy hitting heat sinks, big ish transformer. Not surprised they threw in the towel, especially when you compare the internals to something like a NAD 3020. However it does sound really good!
Mart
The 2000 is built like a battleship inside. God knows what the parts bill would be for it. All those switches, heavy hitting heat sinks, big ish transformer. Not surprised they threw in the towel, especially when you compare the internals to something like a NAD 3020. However it does sound really good!
Mart
- Status
- Not open for further replies.