| Need help troubleshooting a Kasino U100-P [message #27089] |
Wed, 07 November 2018 00:48  |
muddy udders
Messages: 6
Registered: November 2018
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Junior Member |
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I recently picked up a Kasino Club PA head. It works but isn't very loud. All channels seem to be the same no difference, all knobs do what they are supposed to tone wise, Reverb works. I believe I can rule out individual channel boards as they all are equal in volume.
I have the schematics for each board and have been probing the PC900 output board for voltages and everything is close. I see no obvious burned components or bad solder joints. I do see -38v on Q2 BLU which is the base of the 36892. Would this be normal? Schematic shows -.1
I removed both Q1 and Q2 tested them Q2 was hFE=35 Vf=526mV Q1 was hFE=25 Vf=517mV
I put them back in swapping positions and Q2 BLU voltage remained -38v.
If you haven't figured it out yet my skill level is beginner/intermediate. I have built a couple pedals from scratch and in the past built a pirate FM radio station. I know enough to most likely not electrocute myself, no promises though.
Any and all help would be appreciated.
Thanks,
Robert/Muddy
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| Re: Need help troubleshooting a Kasino U100-P [message #27091 is a reply to message #27089] |
Wed, 07 November 2018 13:04  |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Agree with Steve, I think that you have misread the schematic. The -0.1 volt is for the Collector of Q1 not the Base.
Have you tested all of the dc voltages from the power supplies?
I'd want to test your theory about the problem being in the power amp before you do too much work here. All of the preamps are of equal loudness, but they all go through the reverb/mixer board, so the problem could be there as well.
Feed a signal into the power amp at the monitor point. I don't remember if the Casino has a jack there or not, but in any case, there is a point on the pc board. See if you can drive the power amp to a higher loudness level than you are getting from the preamps.
If you don't have a signal generator or some sort of phone app, you can use the signal from another amp or a guitar with a boost pedal of some sort, or even an MP3 player.
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| Re: Need help troubleshooting a Kasino U100-P [message #27095 is a reply to message #27093] |
Thu, 08 November 2018 13:09 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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muddy udders wrote on Wed, 07 November 2018 19:03The DC voltages on the PC900 board were correct for 8v and 39v. I forgot to check the reverb board voltages.
Does this confirm your theory Chicagobill?
Yes, it seems that the power amp is working correctly and the problem is either the reverb board or the low voltage power supply. I don't think that all four preamps would fail at the same time in the same way, unless something unusual happened or was done to the amp.
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| Re: Need help troubleshooting a Kasino U100-P [message #27099 is a reply to message #27089] |
Sat, 10 November 2018 06:21 |
stevem
Messages: 4774
Registered: June 2004
Location: NY
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Senior Member |
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Yes, you have the caps right!
What impeadance is the 4-12 cabinet?
The amp wants a 8 ohm load to output its full clean 50 watts of RMS audio output.
If your 4-12 cab is 4 or 16 ohms then you will only have 25 watts of clean output to work with.
You should be seing some 18 to 20 volts of unclipped audio output at the amps speaker output into a 8 ohm test resistor / speaker load if all is well!
[Updated on: Sat, 10 November 2018 06:24] Report message to a moderator |
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