dbx 166 replacement power transformer?
- aurelialuz
- dead but not forgotten
- Posts: 2012
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- Location: portland, or.
dbx 166 replacement power transformer?
i'm trying to fix this $15 junkshop special dbx 166. it doesn't power up and i know the transformer is not original (wrong mounting hole spacing), so i thought i would start there. only...the transformer spot of the schem available online is left blank, and if it wasn't, i don't think you'd be able to read it anyway since the copy is so bad. the back of the unit reads 117v 50-60hz, and the secondary of the transformer feeds into two LM7915 voltage regulators, so i'm thinking this hammond unit.
questions:
1- does it make more sense to go with one of these?
2 - this 166 does not have switchable power, so they can't be directly the same, but the above studio electronics link seems to indicate that the 166 and the 160x, at least at one time, had the same power needs. can i check to see if the 166 will work with the transformer of my 160x?
questions:
1- does it make more sense to go with one of these?
2 - this 166 does not have switchable power, so they can't be directly the same, but the above studio electronics link seems to indicate that the 166 and the 160x, at least at one time, had the same power needs. can i check to see if the 166 will work with the transformer of my 160x?
"While every effort has been made to ensure optimum sound quality, priority has been given to historic content and importance."
According to page 17 of the 166 service manual, the secondary of the power transformer produces 48VAC, which is rectified to +/- 24VDC, and then regulated by the 7815 and 7915 regulators to +/- 15VDC. You'll need a 48VAC secondary with a center tap to ground, or a 2x24VAC secondary, and connect the windings in series, tying the junction between them to ground.
I'd probably go with this toroidal from Antek:
http://www.antekinc.com/details.php?p=23
It's a dual 22VAC secondary, but once rectified, that will be plenty of DC for the regulators to function, and they'll probably run cooler as they won't have to drop the voltage so much.
I'd probably go with this toroidal from Antek:
http://www.antekinc.com/details.php?p=23
It's a dual 22VAC secondary, but once rectified, that will be plenty of DC for the regulators to function, and they'll probably run cooler as they won't have to drop the voltage so much.
I have one: a stock 110 VAC traffo from a USA dBX 166a. The deal is, I live in Ireland and bought my dBX 166a from a guy in England. It was a US model though so I used to cart around a 220-110 volt step down to run it. Finally the UK dBX people got it together and sent me a 220V traffo, I swapped them, and so I have the 110 Volt sitting on my desk - and I'm not moving back to the US
Anyhow, PM me if you want it ....
Anyhow, PM me if you want it ....
Last edited by CFB4 on Thu Jun 10, 2010 2:08 am, edited 1 time in total.
"It's the most devastating moment in a young mans life, when he quite reasonably says to himself, 'I shall never play The Dane!' "
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It sounds like this might be solved, but a couple of notes:
The 166 is using the unregulated +24 Volts for the LEDs in the curcuit. While the rest of the thing probably works just fine with an unregulated supply more like +/-18, the LEDs mght not be as bright, or light at all, with a lower unregulated supply.
That said, transformers are rated for their loaded RMS Voltages. Peak values will be higher than the RMS, and higher still at less than max load. So if push comes to shove, an 18, 20 or 22V transformer will very likely work. As for size, the specs state 15 Watts dissipation, so look into 15 VA transformers. Amveco, Talema and Antek are the usual suspects.
Looking closer at the manual, they say the unregulates supply can be as far off as +/-3 VDC with 750 mV ripple...meaning about 20 V.
The 166 is using the unregulated +24 Volts for the LEDs in the curcuit. While the rest of the thing probably works just fine with an unregulated supply more like +/-18, the LEDs mght not be as bright, or light at all, with a lower unregulated supply.
That said, transformers are rated for their loaded RMS Voltages. Peak values will be higher than the RMS, and higher still at less than max load. So if push comes to shove, an 18, 20 or 22V transformer will very likely work. As for size, the specs state 15 Watts dissipation, so look into 15 VA transformers. Amveco, Talema and Antek are the usual suspects.
Looking closer at the manual, they say the unregulates supply can be as far off as +/-3 VDC with 750 mV ripple...meaning about 20 V.
- aurelialuz
- dead but not forgotten
- Posts: 2012
- Joined: Mon May 05, 2003 10:46 am
- Location: portland, or.
thanks a lot folks, very helpful information. so in light of the LED issue (har har), would this be a better choice than the dual 22v?:
http://www.antekinc.com/details.php?p=24
how much overage can those regulators take, anyway?
http://www.antekinc.com/details.php?p=24
how much overage can those regulators take, anyway?
"While every effort has been made to ensure optimum sound quality, priority has been given to historic content and importance."
the regs can take a substantial max voltage - problem is that they'll run hotter. Why not try dBX spares - you'll get the exact traffo with correct hole spacing & rating.
"It's the most devastating moment in a young mans life, when he quite reasonably says to himself, 'I shall never play The Dane!' "
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