| Author | Message | ||
     Bob Frye |
I just bought a 112RP-65 amp. There is static in the amp at all but the very lowest volume levels. I noticed that when I jiggle the Bass Pot the static momentarily disappears. I've cleaned the pot with Radio Shack Cleaner but still have the static. I also noticed that when the third ground prong on the power cord is disabled there is a 40 Volt AC reading from chasis to ground. The amp is Chassis No 2165-RP. Any comments or suggestions would be greatly appreciated. | ||
| Terry |
Hi You need to take the amp in to the shop. | ||
| Bob Frye |
I took it in to the shop, paid the guy 55.00 and still have static. Any suggstions would be appreciated. | ||
| Terry |
What did thay say at the shop? & what was done. | ||
| Bob Frye |
The guy at the shop said he cleaned all the pots and changed out a couple of caps. The first time I went to pick it up I tried it out and there was still quite a bit or static. So I told him that I was not satisfied. I called yesterday and he said it was ready to pick up. I didn't test it till I got home and frankly I can't tell any difference than when I took it in. I have been tinkering with it tonight and have narrowed it down to the pre-amp section. When I plug my guitar into the 100 Millivolt jack the static disappears. I pulled the the chasis out of the case a few minutes ago and if the repair guy changed out any caps I can't tell it. As I said before, I can jiggle the bass pot and the static temporarily disappears. I'm thinking maybe the pot is bad or maybe the .22uF capacitor that is hooked to it. Thanks Terry, for responding any other suggestions will be appreciated. | ||
| Terry |
If you think the pot is bad, unsolder the cap and take the pot out. If you can, leave the wires on and take the four tabs off and open them up till you can get the pot apart. See if the arms are ok and spread them open just alittle bit more so you know that they are making good contact. If the race is all right, then the pot should be good. You can check it with an ohm meter if you have one. If ok, put it back together. ((DO NOT USE A SOLDER GUN)) it is too hot!! Clean the jacks 100millivolt and the one next to it. Use some chrome cleaner on a cloth with a small flat blade to get in between the contacts. Put a guitar jack in to open up the contacts. Let me know if this works. | ||
| Bob Frye |
I cleaned the pot. I also cleaned the jacks. Didn't work so I installed a new pot and a new .22uF capacitor, still the same static. Any other suggestions will be greatly appreciated. | ||
| Terry |
If you have a ohm meter, check the resistance on the wires from the pot to the board to see if one is bad. I would move the chips around--take the TLO72 chips, then move them to a different spot that is still using a TL072. Then do the 1458. Keep them in the right place. Maybe one is not making good contact. Have you checked the bias to see if it is correct? And you know the tubes are good? You really have a brain teaser here.... | ||
| Bob Frye |
I tried moving the 1458 chips around with sporadic results. I bought 3 chips at Radio Shack and when I plug one of RS chips in the preamp seciton I get nothing at all. But I tried moving a 1458 from another location and put the RS chip in place of the one I moved and the problem seemed to disappear. Then I exchanged it with another chip and the problem reappeared. Then I thought I'd check the supply voltage to the chips. I'm reading +8.9 and -12.7 to the chips. The schematic says I should have + and - 16 volts from the power supply. Could this be my problem? Maybe the chips do not function properly when the voltage is not exactly right. I'm going to play around with the power supply a bit more to see if that works. Any further suggestions will be appreciated. | ||
| Steve Kennedy |
You might also use a treatment like DeOxit to clean and treat the connections inside the IC sockets as these can corrode and create intermittant noises and problems. The power supply should + and - 15 or 16 volts but at lower levels the imbalance you measure should have little to do with your initial problem. |