Cambridge
Moderators: Slowy, Capt. Black
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remingtonbo2001
- meble-kuchenne.warszawa.pl
Cambridge
Umm...Let me appologize first for being such a pain. Alright, my Cambridge is still dead. When I flip the switch, nothing turns on, but I touched both the large blue capacitor, and the 56 watt chip and recieved a small shock. So I assuming this means power is flowing somewhere through the amp. But, the LED is off, the Power Transformer is cold as ice. My connections are good to go. I noticed that a rectifier, or diode did look a little black, but was that way before. It's Z04. The slow blow fuse looks fine. Connections are good. Could it be the newly installed optocoupler? I don't know. I can't get in to see a TECH until a month from now. That isn't going to do. My guy is out of the states at the moment. He doesn't have a clue, cause he can't look at it. This is frustrating, I wish I hadn't done the mod. Lesson learned. Don't mess with it until it's broken. If anyone knows, let me know. Would pictures help? I just don't know where to go from here. How can I find out what the issue is. Is there a device I can purchase. Thanks again for the help.
Do you have a digital camera or can you borrow one (a good one) to take some macro shots (a mode most good camears have for close up photos) of the circuitry etc.? Posting them here or sending them to your guitar tech if he can check email could help with diagnosing the problem???
I know its not quite the same, but I once had a video card blow on me and looking at it I thought it was just the capacitors, but when I took it to a techie guy he had a close look at it and showed me this little tiny blown Integrated Circuit that I had totally overlooked, but once he showed it to me it was obvious. It showed up very well in photos I later took.
I know its not quite the same, but I once had a video card blow on me and looking at it I thought it was just the capacitors, but when I took it to a techie guy he had a close look at it and showed me this little tiny blown Integrated Circuit that I had totally overlooked, but once he showed it to me it was obvious. It showed up very well in photos I later took.
Righto - I take it you have a circuit diagram (schematic).
First of all you are very lucky - please don't touch the large blue capacitor again because it should store one hell of a belt (yours sounds like residual charge from when it last powered up).
OK from what you describe the power section is down full stop, first if you have a multimeter then do the following (if not pop out to the local electronics shop and get one)
Turn off, pull out the plug and where you touched the large blue capapcitor use a screwdriver with an INSULATED plastic handle to touch the terminals to earth for a could of seconds. You may get a small spark, 'crack' sound don't worry that's normal.
DO NOT PLUG YOUR AMP INTO THE MAINS AGAIN FOR ANY OF THE FOLLOWING! YOU COULD EASILY KILL YOURSELF IF YOU DO!
Next plug something like a light into the wallsocket you use for the amp and check it lights up - if it does all well and fine, if not check at the house fusebox to see if the amp has blown the mains fuse or tripped the circuit breaker.
All fine there? right now check the lead to the amp - one prod at each end of each wire OK? Now the mains on oiff switch (put the meter across the terminals on ohms and the needle should swing down when you flip the switch) OK. Next put the meter across the primary side (where the mains switch goes to and the neutral line) of the mains transformer - should read AT LEAST 300 plus ohms.
Any of the abovce show open circuit then the item will need replacing (sorry for you if the xformer is open circuit - say above 50k's)
Now check the other side of the transformer, the rectifying diodes or any circuitry associated with chopping (you can do the diodes like this - first conenct the meter on the highest ohms one way across the diode then swap the leads over - if they are OK they should read less one way than the other - usually a failrly large amount but one way should be just about infinity/open circuit.
Check the big blue cap by putting the meter across it - needle should slowly but surely swing towards the higher resistance (takes a few seconds) end form the low.
If it reads open cricuit/infinity - replace it.
EVEN IF YOU FIND THE PROBLEM ABOVE - Now what you need is to disconnect the INTERNAL amp power lines (the ht and the low voltage lines inside the amp) and check there are no shorts or low resistance across them - if there are, you need to track them down and repair the circuit FIRST - your power supply will have fialed for a good reason and you need to make sure it's not still there before switching on.
Hope that gets you started - remember to do it all WITH THE MAINS PLUG PULLED OUT AND DISCONNECTED
Yes I know the pros work on amps with the power on but I don't know what level of electrical expertise you have and don't want to be responsible for a fry up or worse.
First of all you are very lucky - please don't touch the large blue capacitor again because it should store one hell of a belt (yours sounds like residual charge from when it last powered up).
OK from what you describe the power section is down full stop, first if you have a multimeter then do the following (if not pop out to the local electronics shop and get one)
Turn off, pull out the plug and where you touched the large blue capapcitor use a screwdriver with an INSULATED plastic handle to touch the terminals to earth for a could of seconds. You may get a small spark, 'crack' sound don't worry that's normal.
DO NOT PLUG YOUR AMP INTO THE MAINS AGAIN FOR ANY OF THE FOLLOWING! YOU COULD EASILY KILL YOURSELF IF YOU DO!
Next plug something like a light into the wallsocket you use for the amp and check it lights up - if it does all well and fine, if not check at the house fusebox to see if the amp has blown the mains fuse or tripped the circuit breaker.
All fine there? right now check the lead to the amp - one prod at each end of each wire OK? Now the mains on oiff switch (put the meter across the terminals on ohms and the needle should swing down when you flip the switch) OK. Next put the meter across the primary side (where the mains switch goes to and the neutral line) of the mains transformer - should read AT LEAST 300 plus ohms.
Any of the abovce show open circuit then the item will need replacing (sorry for you if the xformer is open circuit - say above 50k's)
Now check the other side of the transformer, the rectifying diodes or any circuitry associated with chopping (you can do the diodes like this - first conenct the meter on the highest ohms one way across the diode then swap the leads over - if they are OK they should read less one way than the other - usually a failrly large amount but one way should be just about infinity/open circuit.
Check the big blue cap by putting the meter across it - needle should slowly but surely swing towards the higher resistance (takes a few seconds) end form the low.
If it reads open cricuit/infinity - replace it.
EVEN IF YOU FIND THE PROBLEM ABOVE - Now what you need is to disconnect the INTERNAL amp power lines (the ht and the low voltage lines inside the amp) and check there are no shorts or low resistance across them - if there are, you need to track them down and repair the circuit FIRST - your power supply will have fialed for a good reason and you need to make sure it's not still there before switching on.
Hope that gets you started - remember to do it all WITH THE MAINS PLUG PULLED OUT AND DISCONNECTED
Yes I know the pros work on amps with the power on but I don't know what level of electrical expertise you have and don't want to be responsible for a fry up or worse.
You can't do THAT on stage!