| Author | Message | ||
     Kasper Sørensen (bagudan) Username: bagudan Registered: 11-2009 |
Hi. I have a 410 hd 130, with the 12ax7 in the pre-amp section. When I turn the reverb knob past 3, there is an unpleasant distortion. Not at all loud, but is is there. it is more noticeable when treble is high or the bright switch is engaged.If I just use the reverb at low settings around 2, and roll of the treble, it´s not bad, but I would like to be able to use a lot of reverb occasionally. - Kasper | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
Sorry I didn't see this sooner-I'm freaking old! Anyway, coupe of things pop into my fronz. First is a bad tank. Bad transducers in the tank itself would be my first guess. Also the driver IC's which would be IC5 and IC6 would be my next shot. Look at the voltages on pins 4 and 7 and make sure they are polar opposites-one -, one positive and both the same voltage. If one side is off radically, check the voltage back through to point An the board and make sure they are both equal. More than likely, the voltages would be OK but you never know. If voltages OK, and you sub a known good reverb tank, I'd suspect the IC's 5 and 6. JMHO---Mike. | ||
| Kasper Sørensen (bagudan) Username: bagudan Registered: 11-2009 |
Hi. Thanks for your reply. I already tried subbing in a new tank. it didn´t help. I´ll be trying the IC´s then. There are seven of them. could You tell me wich ones would be nr 5 and 7, when the chassis is open and the potentiometers are facing me? _Kasper | ||
| Kasper Sørensen (bagudan) Username: bagudan Registered: 11-2009 |
I think I figured the IC Numbering out, comparing the pcb to schematic. Then I tried swapping 1&2 for 5&6: No change. But maybe all the IC´s are bad? I´ve found a place on the web that sells lm307H´s. They´re quite expensive. Have 2 pay 30 euros for 2 of them. do you think they are worth a try? The tanks I´ve tried are accutronics 4fb3a1b (input 1475 ohm, output 2250 ohms) -Kasper | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
If you swapped out the IC's and the result is the same, then I would look at the voltages on pins 4 and 7 and see if you have equal + and - voltages. It sounds like one of the IC's is being overdriven. |