Crate Taxi TX15

[Mick Bailey]

Enzo, any chance of re-posting the schematic?

I've got one of these amps with a badly cooked power input board.

[Enzo]

OK, this should work

[Mick Bailey]

Just the job, thanks.

[Enzo]

And for anyone who encounters these, the unit will not run on the charger alone, it MUST have a good battery, and the battery must be charged.

[Mick Bailey]

And for anyone who encounters these, the unit will not run on the charger alone, it MUST have a good battery, and the battery must be charged.

I've got this one back together and noticed it hums in use off the supplied charger unless the battery is fully charged. Is this usual for this amp? PSU ripple at the socket is under 3mv with a fully charged battery, but 580ma with the amp in use and a partially discharged battery - some of that ripple gets carried over. It looks to me like it always needs a charged battery because it's always across the supply, but this is the only one of these I've seen.

[Jazz P Bass]

Something is wrong.

They shouldn't hum.

What input are you using?

And what is the source? (signal generator, guitar?)

[52 Bill]

Something is wrong.

They shouldn't hum.

What input are you using?

And what is the source? (signal generator, guitar?)

Yes, they shouldn't hum, but they do. The charger doesn't have enough capacity to power the amp. If the battery is bad or discharged the amp will hum when powered by the charger.

[Enzo]

The regulator circuit in the amp is what doesn;t have the capacity. All the operating current would have to come through that 180 ohm pass resistor, and it can't. I found out the hard way, thinking it was a problem at first. I used a heavy duty bench supply even, but that resistor killed the voltage. Needs a good battery.

[Mick Bailey]

The little book that comes with the amp is interesting;

"If the amplifier is being played while the charger is connected and plugged into a source of AC power, the battery will neither charge or discharge"

So, given that the battery sits across the DC supply, the circuit can only just maintain the status quo. Or just maintain you playing Status Quo.

[soundguruman]

FYI if this amp does not work:

1. It's almost always a dead battery that will not hold a charge. The battery will last about 3 years.

2. The people who own these amps (usually) refuse to believe that the battery is shot, and try to blame the problem on something else...but it (nearly) always turns out to be a dead battery.

3. The people who own these amps are usually trying to power them with the wrong AC adapter. (as usual) They refuse to buy the right one....because they think that "any" adapter they plug in will make it work (which it won't). GET the correct adapter.

4. NO, the AC adapter WILL NOT power the amp, until it charges up the GOOD FRESH battery.

5. The battery is a GEL CELL that can be bought for $32 at Batteries Plus...GET ONE.

6. BEFORE you go any further, buy A FRESH BATTERY. Make SURE you have the exact correct AC adapter.
Otherwise you are about to waste a lot of time and effort which will produce nothing.

7. Still insist that the battery "must" be good? Stop assuming, and start testing. Typical...

[Jazz P Bass]

Also be aware that the 'replacement' batteries may have a different terminal.

So you may have to crimp on new ones.

[Mick Bailey]

I don't have a problem with the battery (brand new, factory fresh) or the charger (OEM charger specifically for this amp). My question was if they hum while being charged and used at the same time. I think that's established.

[creativejedi]

Lug size on replacement batteries

Also be aware that the 'replacement' batteries may have a different terminal.

So you may have to crimp on new ones.

I have found that the last part of the model number of the battery is either "F1" which is the small lug used by this amp, or "F2" which is a larger lug, requiring replacement of the lugs on the amp to match. So, the model number for the correct replacement battery with the right sized lugs would be "1272-F1". For PowerSonic, which I have found to be an excellent brand, the model number is "PS-1272F1". Most of the manufacturers seem to follow this naming scheme. Hope that helps somebody else.

[soundguruman]

I don't have a problem with the battery (brand new, factory fresh) or the charger (OEM charger specifically for this amp). My question was if they hum while being charged and used at the same time. I think that's established.

YES it hums. Then power supply does not have enough filtering to charge the battery and operate the amp at the same time.
There will be too much ripple.
And that noise increases when the amp is turned up louder as it is charging...

[Jazz P Bass]

Good fact to know.
Thanks!