| K 100 8 [message #26991] |
Sat, 22 September 2018 04:29  |
FeltonPruett
Messages: 5
Registered: September 2018
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Junior Member |
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I came across a '69 K100 8 on Craigslist. YA! My first amp in junior high. It works OK for it's age, the only thing I've found so far is a volume drop when the Trem-Vib (which works) is turned on and when the intensity is turned to 5 o'clock there's more treble. The other thing is when the normal channel is dimed it distorts horribly. A wretched, garbled robot death noise from hell. I'm planning on changing out a lot of capacitors and I've done cap jobs on tube amps... why so many electrolytic caps? I've never seen anything like it. At least it looks fairly easy to work on. Any tips, suggestions or advice on this amp much appreciated.
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| Re: K 100 8 [message #26992 is a reply to message #26991] |
Sat, 22 September 2018 06:23  |
stevem
Messages: 4773
Registered: June 2004
Location: NY
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Senior Member |
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Hello and welcome!
Yes, a bunch more secondary power supply caps and uncoupling caps in a SS amp as compared to a tube !
I would make a list and replace all the electrolytics that are on the 1400 and the 1500 preamp boards since your in there anyway as your taking well less then 20 bucks worth of parts even if you go with top shelf parts!
While you are working on the normal channel I would also replace the first 2 transistors off of the input jack, as one of these could be your issue and if nothing else new current type transistors have a lower noise floor!
Note that on these amps one input jack is briter sounding then the other, not lower gain like the number 2 input as on tube type Fenders and others!
Also note that the 2N5033 transistors on the 1500 board are FET type transistors, not the common bipolar tyoe.
These two boards run off of a positive and negative 8 volt power supply rail that is regulated .
The negative 8 volt rail tracks off of the positive, so if both rails are reading over 8.750 volts there is a issue.
Be very carful with the metal case diode that is held in the clip on the heat sink between the two output transistors as its leads are prone to breaking off at the body if they get moved around too much.
Keep us informed on how it goes.
[Updated on: Sat, 22 September 2018 06:31] Report message to a moderator |
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| Re: K 100 8 [message #26993 is a reply to message #26991] |
Sat, 22 September 2018 12:54 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Welcome!
There are more electrolytic caps in a solid state amp, because the circuit impedances are lower and all of the coupling caps have to have higher values than those in a tube amp. Typical tube amp coupling cap is less than 0.1uF, which would never be an electrolytic.
Again, welcome!
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| Re: K 100 8 [message #27019 is a reply to message #26991] |
Thu, 04 October 2018 06:09 |
stevem
Messages: 4773
Registered: June 2004
Location: NY
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Senior Member |
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The early kustom amps before the B series atleast in terms of the preamp sections are much more tube like with there single rail ( positive and ground ) power supplies.
Early solid state Sunn , Accostic and many many others where the same way , even including the output stage in many of them!
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