I just bought a Roland AC 90 amp to replace my Roland AC100 that is about 30 lbs heavier. I intend to play my acoustic and electric guitars through it; never had any trouble with the AC100. I'm hearing a crackling sound on the AC90 when I use a steel slide on my electric. I never heard that sound on my old amp. Any ideas?
It is because the AC-90 is not grounded. If you look at the power cable, there is just + and -, no ground/earth.
This is because ground is not usually needed when using acoustic guitars/ mikes. If you use an electric guitar, or a slide, there will be problem.
I have a AC60, that does go to ground. No hum. AC90=hum.
Can probably be fixed by attaching new power cable and soldering earth to the chassis, like on the ac60.
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Re: Roland AC90 crackles when using a slide.
Without actually hearing the sound, I can't say for sure, but a few possibilities:
1) The input is being overdriven (not likely if only when using slide)
2) There is some DC on the signal cable that is somehow only seen when using the slide. This should be avoided because of capacitor coupling inside the amp, but may be a problem.
3) bad ground in the guitar itself that is only evident when using the slide.
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I'm not sure what engine you have in your 95 grand am SO I will give you both the 4cyl and 6cyl Specs. Also you didn't ask for the torque sequence. I will include that as well for both. 2.3 DOHC Quad 4cyl: Torque sequence---> front ' 7 3 1 5 9 ' of engine ' 8 6 2 4 10 ' Step 1: torque bolts 1 thru 6 (26 Ft/Lbs & 90 degree turn) Step 2: torque bolts 7 & 8 (15 Ft/Lbs & 90 degree turn) Step 3: torque bolts 9 & 10 (22 Ft/Lbs & 90 degree turn) Recheck final torque in sequence *** CAUTION *** This engine uses "Torque To Yield" (TTY) head bolts that means they permanently stretch during the initial installation. New head bolts must be used when cylinder head is replaced or re-installed in order to obtain proper torque. 3.1 liter V6 Torque sequence--> ' 6 2 3 7 ' ' 5 1 4 8 ' Step 1: torque bolts in sequence to 33 Ft/Lbs Step 2: turn an additional 90 degrees Recheck final torque in sequence *** CAUTION *** This particular engine uses "Torque To Yield" head bolts(TTY) (that means the bolts permanently stretch during the initial installation.) You MUST use NEW head bolts when replacing or reinstalling the cylinder head in order to obtain the proper torque.
This unit has a TDA8920 dual switching class "D" switching amp chip that is thermally protected. If you heat it up it will shut down to protect against overheating. Each side of this is ONLY a 50 watt amp chip HOWEVER they run it at a lower than rated voltage that limits it to about 30 watts per side. Your dial setting number have NOTHING to do with the power limits of the unit. When you use the looper, there are more frequency components added, and all these consume part of the available power. Also make sure the mics and the guitars cannot "hear" the speakers in this otherwise high frequency feedback may occur above what you can hear and use some of the capabilty... hint... reduce the treble boost... The only way to measure the power output is to put a scope or test equipment on the output and compute the power. I suspect you are driving the unit too hard. The unit should give adequate output for a 15 foot square room to a level that *********** could just barely tolerate. Yes, the power amp chip is thermally protected and if you drive it to hard it backs the power down till it cools off.
That will be step 1 to what will probolly become quiet a bit of problems. I'm not huge on this unit but generally speaking if you opened the chassis your going to see a few burnt components (rectifier,diodes,transistors). But lucky 220 hits so hard it's usually just a replace the stuff you see burnt (get schematic if possible) it's a pretty straight forward repair.
I would expect there is bad soldering or a circuit board crack. Inspect the soldering aound the leads, especially pots and heavy components. Finding all the retaining screws can be frustrating. Expect the screws for the handle to also attach to the amp chasis. They are often hiodden under plastic caps.
I don't have the exact schematic... however sometimes they have RF bypass capacitors to ground on the balanced input lines and one side gets shorted. The schematic I do have is for an AC100. It shows a rather unconventional input circuit. You can download it here and it MIGHT be close to your unit:
your sound process digitaliser has burned out the crackling should have warned you as to the fault and had it replaced (fixed) right away this is a simple repair but does need to be done by an electronics tech
All readings in ft. lbs.
Engine Displacement Liters (VIN)
Cylinder Head Bolts
Main Bearing Bolts
Rod Brearing Bolts
Crankshaft Damper Bolts
Oil Pan Drain Plug
NA: Not Available
① Step 1: Long bolts: 46 ft. lbs.
Step 2: Short bolts: 43 ft. lbs.
Step 3: Long bolts an additional 90 degree turn
Step 4: Short bolts an additional 90 degree turn
② Center bolt spec shown; Pulley-to-hub bolts: 37 ft. lbs.
③ Bolts: 17 ft. lbs.
Nuts: 17 ft. lbs.
Studs: 9 ft. lbs.
④ Step 1: bolts 1-8; 40 ft. lbs.
Step 2: bolts 9-10: 30 ft. lbs.
Step 3: An additional 90 degree turn
⑤ 15 ft. lbs. plus 90 degrees
⑥ 18 ft. lbs. plus 80 degrees
⑦ 129 ft. lbs. plus 90 degrees
⑧ 15 ft. lbs. plus 45 degrees
⑨ Nuts: 18 ft. lbs.
Studs: 97 inch lbs.
⑩ Nuts: 31 ft. lbs.
Studs: 97 inch lbs.
⑪ Step 1: Long bolts: 2 ft. lbs.
Step 2: plus an additional 155 degrees
⑫ 15 ft. lbs. plus 70 degrees
⑬ 18 ft. lbs. plus 100 degrees
⑭ 74 ft. lbs. plus 125 degrees
⑮ 39 ft. lbs. plus 25 degrees
⑯ Bolts: 89 inch lbs.
Nuts: 89 inch lbs.
Studs: 53 inch lbs.
⑰ Bolts: 89 inch lbs.
Studs: 12 ft. lbs.