This single board is 2 amps in one. Two separate PSs, SG3525s, and outputs. Its dual mono amp. Looks like the board<s> are actually 2 channel boards that are bridged internally and then sent out as 2 channel. Seems like a 4-channel amp internally bridged. There are a bunch of faults such as all the missing and mis-matched outputs; I'll be able to easily work through, but I have a question pertaining to regulators.
When I first powered on this amp, only the LEFT side of the board produced output. The RIGHT side of the board had rail voltage but no regulated voltage hence no audio. Thats when I saw someone had removed the 15v regulators from the RIGHT side of the board. The Left & working side is using LM340T15 and LM7915CT - which I don't have any. I have LM337 and LM317 but those are not fixed +-15v.
So to be sure the non-working channel would possibly work; I temporarilly tied that side to the working regulators - and it worked. Both channels now produce audio. (Thin RED and BLACK wire)
Can I leave it like this? Amp Center Taps are tied together anyhow via the purple wire from the right Toroid to the Left non-bridging terminals. If so then I have all the parts to restore this amp fully, but I'll have to keep the regulated voltage tied, or just go ahead and order 15v regs.
Photo coming.
When I first powered on this amp, only the LEFT side of the board produced output. The RIGHT side of the board had rail voltage but no regulated voltage hence no audio. Thats when I saw someone had removed the 15v regulators from the RIGHT side of the board. The Left & working side is using LM340T15 and LM7915CT - which I don't have any. I have LM337 and LM317 but those are not fixed +-15v.
So to be sure the non-working channel would possibly work; I temporarilly tied that side to the working regulators - and it worked. Both channels now produce audio. (Thin RED and BLACK wire)
Can I leave it like this? Amp Center Taps are tied together anyhow via the purple wire from the right Toroid to the Left non-bridging terminals. If so then I have all the parts to restore this amp fully, but I'll have to keep the regulated voltage tied, or just go ahead and order 15v regs.
Photo coming.
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1 new LM7915CT is only 30cents.. that same for the LM340T15, you could also take LM7815CT..
The way you propose the AMP will not survive..
Fix that the right way in the way of Buying these Regulators, and soldering them into place..
Who ever build this amp had a reason to use the way it is designed. I would follow this reason.
The way you propose the AMP will not survive..
Fix that the right way in the way of Buying these Regulators, and soldering them into place..
Who ever build this amp had a reason to use the way it is designed. I would follow this reason.
Not those things at all. Its partially because I've not seen many amps like this with 2 amps inside. As far as I can tell there is only one 8-pin IC that needs the +-15v on the right side. At the time of my temporary modification it seemed kind of a 'waste' to have two sets of regulators if only for that one IC. The left board is handling all pre-amp activities and the right board has none.
I'll order some new regulators for this amp. Thank you
I'll order some new regulators for this amp. Thank you
Getting back into this one. I placed new regulators and also replaced ALL output transistors.
The PS seems to be in-tact, using IRFZ34 with 470ohm gate resistors.
To me the PS drive may be a little weak but it may be ok? The outputs are what failed in this amp I believe. I varied the supply voltage between 10vDC and 14.4vDC and amperage draw and waveform at the gates look to be alright. Amp idles at 1.04A with no load and the board out of the sync.
I think this one is fixed, but is it strange that the gate resistors are 470ohms? That seems bit high to me but maybe thats OK with the IRFZ34?
The PS seems to be in-tact, using IRFZ34 with 470ohm gate resistors.
To me the PS drive may be a little weak but it may be ok? The outputs are what failed in this amp I believe. I varied the supply voltage between 10vDC and 14.4vDC and amperage draw and waveform at the gates look to be alright. Amp idles at 1.04A with no load and the board out of the sync.
I think this one is fixed, but is it strange that the gate resistors are 470ohms? That seems bit high to me but maybe thats OK with the IRFZ34?
The gate resistor value is dependent on the FET and the deadtime. If the FETs aren't heating up at full duty cycle, the drive is OK.
Theres no supply regulation in this amp from what I can tell.
Thank you. Amp is back together going to gently test it out tomorrow.
Thank you. Amp is back together going to gently test it out tomorrow.
This applies to all amplifiers.
I think this amp does have regulation (I could be wrong) but it's PAM (like Orion) instead of PWM.
I think this amp does have regulation (I could be wrong) but it's PAM (like Orion) instead of PWM.
Thank you.
This is one very hungry for current amplifier. I've not seen an amp actually pull this much current for what its able to output to speakers. Currently have it hooked up to 2x15" woofers at 2-ohms a piece. Actually the amp may not be rated for this type of load. Amperage draw pulls out to about 120A from the bench. I'm actually affraid to let it pull more atm. Seems a little off to me as its actually not getting very loud out of the speakers. The quality of the audio is OK.
I read in the user manual that this amp gets (2?) 35A fuses. I think this one might be fixed but the efficiency is pretty low.
The waveforms on the IRFZ34 look to be OK at full tilt. This amp does PAM.
This is one very hungry for current amplifier. I've not seen an amp actually pull this much current for what its able to output to speakers. Currently have it hooked up to 2x15" woofers at 2-ohms a piece. Actually the amp may not be rated for this type of load. Amperage draw pulls out to about 120A from the bench. I'm actually affraid to let it pull more atm. Seems a little off to me as its actually not getting very loud out of the speakers. The quality of the audio is OK.
I read in the user manual that this amp gets (2?) 35A fuses. I think this one might be fixed but the efficiency is pretty low.
The waveforms on the IRFZ34 look to be OK at full tilt. This amp does PAM.
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Meh. Here is a confirming video of sort. Current hungry.
1991 Precision Power 2300AM Amp Dyno Test PPI Art - YouTube
1991 Precision Power 2300AM Amp Dyno Test PPI Art - YouTube