tedsorvino 3/13/2018 5:45 PM
Carlsbro Glx documentation
Hi I'm using a Carlsbro Glx 80 for about 20 years now. It's well maintained but suddenly the preamp section on both channels (I checked the other sections) went faint. I can't figure out what could have gone wrong since all the mechanical parts work ok....Leads, pots, etc. The power amp section and the send return along with the reverb section work great. I 'm not sure how it is constructed so I'm looking for any relevant or specific documentation (service maual, schematics etc.) of any model of the Carlsbro GLX series. Thanks in advance
 
g1 3/13/2018 5:57 PM
Connect the send to the return with a patch cord. Does the proper volume come back?
 
tedsorvino 3/13/2018 6:06 PM
Thanks G1 for the help...but no. It doesn't come back.
 
g1 3/13/2018 6:22 PM
Ok, you said the send and return both work fine. If the power amp section works fine when you go into the FX return, then the send must be weak, no? Have you connected the send into another amp's return?
 
Jazz P Bass 3/13/2018 11:09 PM
As always, start at the power supply. If the opamp supply is flaky, so will the output of the preamp be. [ATTACH]47580[/ATTACH]
 
tedsorvino 3/14/2018 4:36 AM
thanks for the documents Jazz P Bass. Any ideas about voltages?
 
tedsorvino 3/14/2018 4:37 AM
Yes g2. Tested that. The send sounds weak in another amp too.
 
tedsorvino 3/14/2018 5:34 AM
[QUOTE=tedsorvino;482905]Yes g2. Tested that. The send sounds weak in another amp too.[/ I mean g1. Sorry about that....
 
Jazz P Bass 3/14/2018 9:58 AM
[QUOTE=tedsorvino;482904] Any ideas about voltages?[/QUOTE] The low voltage supply is marked right on the schematic. +15 and -15 Vdc. Check the Volts ac on the supply also (for opamp supply, it should be zero) [ATTACH]47582[/ATTACH] [ATTACH]47583[/ATTACH]
 
tedsorvino 3/14/2018 11:53 AM
thanks a lot Jazz P Bass. i will try to test them. Is there any layout of the boards you've sent since I think the schematics are quite different to the boards I have, and it would help to find differences and similarities in an easier way. My Input one is PC02227L x 1 and the Master one is PCO2228L x 3. I 've got no id for the Power one. Cheers.
 
g1 3/14/2018 12:06 PM
Looks like the loop is between IC6A and IC6B, so if return is working right, then the IC supplies should be ok as well, but check them anyway. TR16 is a mute.
 
tedsorvino 3/14/2018 12:47 PM
Thanks g1. Yes the loop is between these two ICs. What about that transistor? I can't see any TR16 transistor on any of my boards. They are slightly different to the schematic one (I ve got no Mute on my amp) . Will check the ICs tomorrow.
 
g1 3/14/2018 12:58 PM
The mute is not something you will have a user control for. It's an automatic mute that is engaged while the unit is powering up, so you don't get a big turn on thump. If it is defective it will reduce or kill the signal. The schematic is not a match?
 
Jazz P Bass 3/14/2018 4:10 PM
Can the OP provide any circuit board numbers? There were about 5 different versions of this amp.
 
tedsorvino 3/15/2018 1:52 AM
[QUOTE=Jazz P Bass;482950]Can the OP provide any circuit board numbers? There were about 5 different versions of this amp.[/QUOTE] Input board is PC02227L x 1, Master board is PCO2228L x 3 and the Power board is PC01863T x 3. All of them JBR 18/3/1993. The Lo Voltages are around the PL1 on this one and they are 39V DC and -39V DC. Otherwise the power transformer gives 30V AC.
 
tedsorvino 3/15/2018 1:53 AM
[QUOTE=g1;482929]The mute is not something you will have a user control for. It's an automatic mute that is engaged while the unit is powering up, so you don't get a big turn on thump. If it is defective it will reduce or kill the signal. The schematic is not a match?[/QUOTE] No the schematic is different