Q2 and Q61 are fine. They were replaced because Q2 shorted (base and emitter were what was shorted). I still haven't figured this out yet. Can somebody please explain how this regulator works. Doesnt look like its exactly the same as the -18 side. What components make up this regulator? I might just replace all of them... Also I cant find any info on the "THAT 2810LC" chip right next to this. What is it for and is there a data sheet online for it?
When you checked the zener diode that's connected to the base of the two regulator transistors, did you pull it and check it to see if it was leaking (passing current more like a resistor than as a diode)?
How much voltage is there across the resistor that's feeding voltage to the zener?
'THAT' is the part number of the IC but I can't find anything on it either. The other numbers are likely a production code. The IC is used for the remote level control.
If I remember correctly, it's a simple shunt regulator with a series pass current boost transistor (actually two transistors in parallel in this amp).
As a side note, do not power the amp with the zener out of the circuit.
How much voltage is there across the resistor that's feeding voltage to the zener?
'THAT' is the part number of the IC but I can't find anything on it either. The other numbers are likely a production code. The IC is used for the remote level control.
If I remember correctly, it's a simple shunt regulator with a series pass current boost transistor (actually two transistors in parallel in this amp).
As a side note, do not power the amp with the zener out of the circuit.
All that is powered off the +18 is the 5 OP Amps correct? I did not pull the diode yet but that is the next step. I pulled all 5 of them so that I wouldent kill them while playing with this.
OK, I pulled the diode and I think it is toast. I get a reading in both directions for the diode test on my multimeter. What is the 6 volt zener diode below it for? Its connected to the 18 volt zener diode on the +18 side.
I got ALL the same things you did! Even after changing the diode and the transistors, etc, i STILL get the odd values and one resistor heats up quickly. Believe it or not, i haven't fixed it yet, it's on the 'to do' pile and has been for a long time!
Hopefully you resolve it - means i can too! You'll have to let us all know what ends up being the culprit and what you replace !
Thanks
Aaron
Hopefully you resolve it - means i can too! You'll have to let us all know what ends up being the culprit and what you replace !
Thanks
Aaron
Any luck yet? Haven't had any time to mess with mine but I am almost sure the diode is bad. Think I should replace all the op amps while I am buying parts or do you think they should be OK? They don't appear to be shorted...
what was the part number for the diode? I replaced mine but it didn't make any difference for me 🙁
Nice find.
I wrongly assumed that the numbers were a date or production code because they have been different on various amps. It looks like they changed from the 2155 to the 2180 when the 2155 went out of production.
http://www.thatcorp.com/datashts/2150data.pdf
I wrongly assumed that the numbers were a date or production code because they have been different on various amps. It looks like they changed from the 2155 to the 2180 when the 2155 went out of production.
http://www.thatcorp.com/datashts/2150data.pdf
Not to threadjack, but...
Is there any source for further information on the 500D? Mine's failed in a slightly different way, and I'd love to get some actual documentation for it. The thread has been helpful so far, but I'd like to be able to troubleshoot mine without posting every step of the way.
Is there any source for further information on the 500D? Mine's failed in a slightly different way, and I'd love to get some actual documentation for it. The thread has been helpful so far, but I'd like to be able to troubleshoot mine without posting every step of the way.
In what way did the amp fail (outputs, regulators, power supply FETs...)?
If no one volunteers any info, start a new thread and we'll try to troubleshoot it.
If no one volunteers any info, start a new thread and we'll try to troubleshoot it.
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