Alpine 3545 squared

[Dr Zeus]

$30 is no big deal, Its just that I thought I could use something similar and available. I'll likely order the right ones for this amp once I figure out if any further faults are present. I'm going to try the U1620x rects tonight to see.

 

[Dr Zeus]

I put the U1620x rects in and the amp powered up with ~0.035 voltage across the speaker terminals. This amp seems to draw pretty hard when first powering up - my 10A power supply strains for about ~2 seconds in protection before it finally kicks on. I dont have an ampmeter but am thinking of retro fitting one into this supply.

Would it be a cap that could be causing the power-on strain? It could also mean something that was possibly causing this amp to go into over-heat mode. Q602 and D601 are off the PCB, and the 494 has pins 4 & 7 jumpered.

I can probably test the rest of this amp.

Wouldnt you believe; this amp has the same exact power supply white-noise as the other Alpine 3545 I'm working on. /shrug

 

[Perry Babin]

There may be a bit of a soft start that is disabled with 4 and 7 shorted.

 

[Dr Zeus]

OK that would make sense.

This amp produces no output; but I'm not surprised as its gain controls are broken - they twist around 360 degrees round and round. I'm trying to source somehting equivalent on a parts amp... but the wierd thing is this amp has a 'fixed' bypass switch for the gain control. Its meant for setting the gain to a certain fixed level; possibly about 1/3 the way up. Still, it doesnt have any output. I'm poking around though.

EDIT: Nevermind much... RCA jacks are making very bad connections. Spare-parts amps are good.

 

[Perry Babin]

When set to fixed, the gains are out of the circuit. Do you have audio on the output pins of the op-amps on that board?

 

[Dr Zeus]

EDIT: Nevermind much... RCA jacks are making very bad connections. Spare-parts amps are good.

 

[1moreamp]

All these older NPN transistor based PWM supply's drew huge inrush start up currents. This was normal for them back then. Back then a ten amp supply would just barely turn some amps on and in some cases cause them to falsely shut down from excessive V drop on the supply. I always use a 20 amp supply with variable current control. A larger cap on the supplies output is a cheap fix that can be switched in and out of circuit as needed.
like PPI600 says you always turn it down....

 

[Dr Zeus]

I found the RCAs just needed to be re-soldered to the verticle board. The amp now produces clean sound from both channels; and even the gain controls work well enough to perhaps just leave alone, and whoever uses the amp will likely have to set the gain carefully or just use the 'fixed' gain switch.

The gain pots are 50k just in case though.

I put D601 and Q602 back i nthe circuit, as well as removed the jumper from 4-7 of the 494. The amp powers up just fine without straining my power supply. Looks like the over-heat LED was ultimately caused by the faulty rectifiers.

Really, all this amp needs are a set of the correct value rectifiers and a little tune-up of the dials. Looks like $30 will be well spent indeed! Two Alpine 3545 amps fixed for ~$30 and a boat load of time. Is that a level 5 or level 2 repair?

 

[Perry Babin]

This is level 1/2.

Nice to see that you've been doing some reading.

 

[stumpjumper]

2 alpine 3545 for sale

Most early Alpines had individual screws per transistor. Makes it a real pain to work on but it is so worth it in the end in my opinion. Love these old Alpines

Would you be interested in buying 2 like new 3545 alpine amplifier


quadboy75@live.ca