13-03-2014, 05:18 PM
lawrence. re comments regards caps charging it sounds obvious when you explain in simple terms. refugee i will try what you said with 3 volts dc and then 5 keep you informed. thank you richie
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A request from a non member
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13-03-2014, 05:35 PM
No problem Richie, if there is anything your unsure of just post a question on the forum, one of the members will probably give you an answer or explanation.
Lawrence.
13-03-2014, 08:11 PM
refugee powered up with the 5 volts for about ten minutes nothing on the large board amp circuit or front panel got warm. i checked every cap resistor transistor everything. next please my power supply goes up to 12 volts dc
lawrence i was going to do the ohm checks you mentioned after powering up with 5 volts for ten mins will this charge the caps and ok to do the checks. thank you richie.
13-03-2014, 08:24 PM
Was there anything loose in the cabinet?
I was thinking last night that there could have been caused by a foreign object that is either a fixing part that has come loose or something that has slipped in between the keys.
13-03-2014, 08:37 PM
(13-03-2014, 08:24 PM)Refugee Wrote: Was there anything loose in the cabinet?there was a couple of screws loose in the main cabinet on the shelf where the amp is i removed them. i know that they kept the top circuit board at the back of cabinet in pics which stands upright. i removed rest of screws and checked that board but no signs of defects. that's why it's leaning forward supported by cassette cases. I am convinced that this item will work if i replace the resistor
13-03-2014, 08:51 PM
It is looking more like it.
When it was used with a guitar did the guy take the back off for any reason?
13-03-2014, 09:12 PM
(13-03-2014, 08:51 PM)Refugee Wrote: It is looking more like it.I believe that either he did. Or they have got an engineer he saw the problem took out the resistor to match up then found it would be to expensive to attempt to repair bear in mind you've all said the resistor is not the initial cause. any clues to what size resistor yet. I am thinking of trying a 20 watt wire wound ceramic/cement any idea what ohms i should try. i looked at higher wattage but they are alloy cased and need a heatsink i don't think it had a heatsink.
13-03-2014, 09:20 PM
"lawrence i was going to do the ohm checks you mentioned after powering up with 5 volts for ten mins will this charge the caps and ok to do the checks."
No, if you need to check for leakage in a capacitor by an ohms test the capacitor should be discharged first (power off of course) Then you need to disconnect one end of the capacitor from the circuit to get a reliable resistance reading. The reason for discharging the capacitor is that any voltage charge that might be retained in the capacitor can be many times the voltage of the internal battery in the test meter. If a capacitor is across a low resistance circuit the capacitor should discharge more or less straight away, if it's across a high resistance circuit then the discharge time will be longer, how much longer depends on the value of circuits resistance and the value of the capacitor that is charged up. You also need to be aware that testing for capacitor leakage on a standard multimeter isn't by any means conclusive, in many cases the test voltage output from a meter set to measure ohms will be far less than the working voltage of the capacitor under test. Anyway I'm digressing, the fact that nothing is getting warm indicates so far so good with your voltage test If you need to know how a meter works and what the electrical properties of a capacitor are then click on the link below, it''s all in there somewhere, the link is worth saving: http://www.allaboutcircuits.com/ Lawrence.
13-03-2014, 09:24 PM
I would go for 220 ohms and work down in value from there.
We need a photo of the board that is fed by the missing resistor so that we can see if there is a regulator on there. The bit we need to see is the area around the connector that carries the power to the board from both sides. We are also looking for signs of a foreign object having shorted and made a little mark on the solder.
13-03-2014, 09:33 PM
lawrence i will go on that link.
refugee i will try the 20 watt 220 ohm resistor and see what happens. i will bring the mains voltage up slowly. i looked on maplins site the highest shown is 10 watt so i may have to wait a while ordering of net. thank you all richie |
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