the beta of the one NPN transistor in the middle of the circuit is not an issue. I simulated with a beta of 50, 100, 150 and the output DC bias point only changed by about 150 mV.
The right most transistor stabilizes the quiescent point of the circuit. You may have to readjust the variable resistor to hit the indicated -12 V on the collector.
Please note that the indicated -20 V at the bottom of the variable resistor is a typo. That voltage should actually be positive 20 V.
Update My Dynaco
Akitika GT-101 Audio Power Amplifier Kit
The right most transistor stabilizes the quiescent point of the circuit. You may have to readjust the variable resistor to hit the indicated -12 V on the collector.
Please note that the indicated -20 V at the bottom of the variable resistor is a typo. That voltage should actually be positive 20 V.
Update My Dynaco
Akitika GT-101 Audio Power Amplifier Kit
How about this?
Assuming that -12V on Q25 collector is correct.In my view it should be about halfway between zero and -22.5 volts,which it is.
All currents indicated are very approximate!
There's still that very odd Ube of Q25....
By the way-there are TWO module type III.One that ends with -7 and this that ends with -8.
Assuming that -12V on Q25 collector is correct.In my view it should be about halfway between zero and -22.5 volts,which it is.
All currents indicated are very approximate!
There's still that very odd Ube of Q25....
By the way-there are TWO module type III.One that ends with -7 and this that ends with -8.
Attachments
When taking a closer look at the complete schematic-at least up to the volume pot,I discovered to my horror that they have named the modules differently depending on which channel they are used in,despite the fact that they are-and should indeed be-exactly the same!That explains the two variants of a certain module.
The phono preamp is somewhat complicated.At first there's a module type I,followed by selection of correction-in this case a passive RIAA network-followed by a module type II.The signal has now been raised to the same level as tape,tuner,aux and can be fed to the balance and volume pots.
The phono preamp is somewhat complicated.At first there's a module type I,followed by selection of correction-in this case a passive RIAA network-followed by a module type II.The signal has now been raised to the same level as tape,tuner,aux and can be fed to the balance and volume pots.
citation A transistors
hello, i realize this is an old thread, but if anyone can help id really appreciate it. i have a citation A. all electrolytics have been replaced. now im having transistor trouble. the transistor numbers on the amp boards are hkt 10 which is a pnp germanium hkt 11 which is an npn silicon. and hkt 12 which is a pnp germanium. im not sure if this is supposed to be. but it is this way on all seven amplifier boards. the emitter follower boards have two pnp germaniums and two npn germaniums. the preamp does work however there is distortion at higher levels and when i turn either bass knob up at any point passed half the signal cuts in half and becomes distorted. im wondering if this pre was designed to use these npn silicon devices. or if they to are supposed to be germanium. any insight would be greatly appreciated.
hello, i realize this is an old thread, but if anyone can help id really appreciate it. i have a citation A. all electrolytics have been replaced. now im having transistor trouble. the transistor numbers on the amp boards are hkt 10 which is a pnp germanium hkt 11 which is an npn silicon. and hkt 12 which is a pnp germanium. im not sure if this is supposed to be. but it is this way on all seven amplifier boards. the emitter follower boards have two pnp germaniums and two npn germaniums. the preamp does work however there is distortion at higher levels and when i turn either bass knob up at any point passed half the signal cuts in half and becomes distorted. im wondering if this pre was designed to use these npn silicon devices. or if they to are supposed to be germanium. any insight would be greatly appreciated.
Citation A transistor troubles...
Hi Everyone,
I was the originator of this "Citation A" thread. Just to give an update of my transistor trouble that may help some of you. My transistor turned out not being defective. Transistors usually work or don't work. One or the other. Not part time. Mine would work when I turned it on but after a short time it would start hissing or fizzing. This only affected the one channel. After exhausting all possible avenues of replacement I decided to pull the transistor and look through old transistor replacement manuals to no avail. Since I didn't know what the particular transistor was, I had a difficult time. I decided to give up and put the transistor back in the board. Much to my surprise it worked and continued to do so without any further problems. I came to the conclusion that more than likely it had a cold solder joint and when I reinstalled it with new solder it solved the problem. This preamplifier didn't get much attention when I bought mine and did an in-depth review of it's qualities. Now they are getting the attention they deserve. It's a fantastic early transistorized preamplifier (in fact the first one) work of art. Check those solder joints. Enjoy!
Hi Everyone,
I was the originator of this "Citation A" thread. Just to give an update of my transistor trouble that may help some of you. My transistor turned out not being defective. Transistors usually work or don't work. One or the other. Not part time. Mine would work when I turned it on but after a short time it would start hissing or fizzing. This only affected the one channel. After exhausting all possible avenues of replacement I decided to pull the transistor and look through old transistor replacement manuals to no avail. Since I didn't know what the particular transistor was, I had a difficult time. I decided to give up and put the transistor back in the board. Much to my surprise it worked and continued to do so without any further problems. I came to the conclusion that more than likely it had a cold solder joint and when I reinstalled it with new solder it solved the problem. This preamplifier didn't get much attention when I bought mine and did an in-depth review of it's qualities. Now they are getting the attention they deserve. It's a fantastic early transistorized preamplifier (in fact the first one) work of art. Check those solder joints. Enjoy!
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