Bose L1, PS1 help needed – have official Bose Repair Manual

[Ricky_Vato]

Hi folks. I have had it with Bose flatly not supporting the older units. My L1 Model 1 went out and they wanted me to pay $899 one day, and then $999 another day, and finally someone there said, $1299 to upgrade to a Model 2. Nope, not paying more for less. Lucky for me, I found a place that repaired the Aux Power Supply, and the Amplifier in a two day turnaround. It cost $400 with a warranty. For those who think this is a better way to go and keep what you have, try Orange County Electronics Service, 23284 Del Lago Dr., Laguna Hills, CA 92653, (949) 768-0861

[Westrek]

I just finished a successful repair on one of these units. The aux power supply not functioning. In this case it was 2 shorted diodes. D602 and D607. Also note that the output voltages will not be correct unless the unit is completely reconnected with the other boards.

[Ricky_Vato]

I just finished a successful repair on one of these units. The aux power supply not functioning. In this case it was 2 shorted diodes. D602 and D607. Also note that the output voltages will not be correct unless the unit is completely reconnected with the other boards.

Wow. Glad that worked out for you. In my case both the Aux supply AND the amplifier went out. I did not mind the cost as I saw the parts replaced and the fact the turnaround was two days. Plus, I have a warranty on the two most crucial issues with the L1s. The sad part was I loaned the system to a friend and he did not tell me it went out on his show much less what he did to cause the damage. He just brought it back and two weeks later when I needed it, it was dead. Lessoned learned.

[alexradium]

i think that Bose is an indian word for S***,because that's what good hifi world became when their reps started flooding houses with those lame cubes,sorry for the rant,similar to AP*le today.

[scalefreak]

i think that Bose is an indian word for S***,because that's what good hifi world became when their reps started flooding houses with those lame cubes,sorry for the rant,similar to AP*le today.

I've got one of these bloody things on my bench now. Just replaced q503/504, r502, r509, r510, z2503 & z2504. Still dead in the water. I'm going to check d602 / d607 as westrek mentioned. I had to get a little upset just to get bose to send me a schematic. I guess I should have consulted with Google first.

[Ricky_Vato]

I've got one of these bloody things on my bench now. Just replaced q503/504, r502, r509, r510, z2503 & z2504. Still dead in the water. I'm going to check d602 / d607 as westrek mentioned. I had to get a little upset just to get bose to send me a schematic. I guess I should have consulted with Google first.

scalefreak, I am positive you will get the unit working. I notice people are slowly going back to the Model 1 Classic and buying up the ones they can find. I bought a non working Classic power stand for $199 off Ebay with free shipping. I will have it checked out, repaired, and hold onto it as a spare. The Classic PS1 can power other speakers if need be. Better option than 3 Packlites.

Sorry Bose. The Classic was the best with a 4 channel mixer, 3 amps, and louder acoustic output. To charge more for a Model 2 with one input, require a separate mixer, 1 less amp, lower acoustic output is not a good buy. I see a lot of Compacts, Model 1-S, and Model 2s for sale on Craigslist in my area. Has to be a reason.

[Westrek]

So, one of the 27 volt supplies is not functioning?

[Ricky_Vato]

scalefreak, did you get the unit repaired? I would like to see a movement of people sharing their repair stories to help others.
I paid to have my Model 1 repaired here in Southern California, and found out online there is a repair place in the state of Georgia. Maybe there is a place on the East Coast of the U.S. This would be good info for others to know. I bought a non working Classic L1 off Ebay for $199, and took it to the shop where I took my Model 1. The guy repaired that one in two days as well. He said the Classic is the best made and designed L1 with 3 discrete power amps and multiple in/outs. He should know with over 50 years repairing high end and rare equipment. With the repaired Classic PS1, I now have the equivalent of 3 paklites and a 4 channel mixer.

[keyboards2]

I just finished a successful repair on one of these units. The aux power supply not functioning. In this case it was 2 shorted diodes. D602 and D607. Also note that the output voltages will not be correct unless the unit is completely reconnected with the other boards.

Got one of these beauties on my bench right now...gonna see what it takes to get it back out on the track. Been a component level tech for close to 40 years now; shouldn't be an issue to find which component let out the magic smoke.

I'll report back to the forum what I find.

[Parksy]

Hi Everyone my first post on this forum.
Im an engineer trained on valves in the 70's still fixing stuff.
The PS1 is an awesome piece of kit, I have 2, with little more than a service manual i have fixed them quite a few times now.
1st time changed all the 27+/- DC output power supply capacitors which had bulged C504, C505, C506, C522 all 2200uf 35v i used the 105 degree C type. (I should have changed all capacitors on this board at this point)..
2nd time i had a 27V +/- psu failure and had to change 4x IRF840, 4x 18v zener, 4x 51ohm, 2x 1k, 2x 1N4006 all on the DC power input side of the 27volt DC PSU.
3rd time (caused initially by a power generator fluctuation) i had 1 of the 27 volt power supplies fail on the input side again this took out both of the NTC thermistors TH601/602 SCK0512 on the power filter board, the fuse and 3 of the audio amplifier output chips U804, U805, U806 in the centre channel, the capacitors, some looking bulged were changed also, this was the lower line array speakers channel.
4th time (i had shorted out the thermistors in a hurry to get it running) I used it at a beach party with that dodgy generator again, 2 of the 27 volt power supplies failed at once on the DC input side again, 2 of the power supply 27 volt +/- rails were low after repairing them 10-15v but this time the 24 volt rail from the auxiliary power was at only 18v (all were low 3.6, 4v, -11, +12 and 18v) which crept up a little until a threshold was crossed and all of the 27volt power supplies came back up.
It was at this point i accidentally (while doing a meter check to trace the problem) shorted pin 6 and 7 of the on the aux power supply board UC2843 and the whole thing lit up like guy fawkes night should have.
Something on that board was still holding the drive voltages down, i had changed all the aux board caps, optocoupler IC602 is on but not IC606, but i have a few more parts to change now before i find out what it is. will keep you posted.

[Ricky_Vato]

Parksy, thanks for the info and experience. I hope it helps others.

[Aloon26]

Hi drewl, do you still have the Aux PSU ??

[Dalton]

I'm new here, and I've got a 35+ year background in electronics' repair, (well back when their was money to be made Now its a throw-away society Anyway I've been putting it off for some time, but I have two Classic power stands I need to look at, a non-working one was thrown in for free with 1/2 an array, when I purchased a complete used system off ebay, about 4 years ago, and I never tested that one because I had another new system, so I should dig it out and check it,,,, I've had a lot off non-working gear show up and somehow fixed itself in transit....? The other used system I ran for about 5 or 6 hours and it craped on me and at the time I was working 24/7 in the oilfield, no time for anything so I just put all of them in their roadie bags, and kind of forgot about them as theirs nothing going on here in the armpit of Oklahoma,,,, Music wise. What got me thinking about them, is I have tons of tube amp's, and I'd got an Boss GP-10 awhile back, plus I have a Fishman Triple play, and I was thinking of wiring an line array to an SS Amp and have one half of the Line array on each side off a 4x12 cab for the GP-10 and the FTP... but then I'd need to get the sub in there also, That's how I came upon this forum,(looking for the array pin outs) so now I'm gonna dig my Bose's out and see what I've got going on. So Parksy,,, all that was cause from a power generator? Who would a thought. Damn I bought a new 10,000 watter and was thinking of getting some old buddy's together this spring and jamming-out on the back forty, now I'm not sure. This forum and these post may just be the nudge I need to get those two working though..

[Dalton]

Sorry for any typo's,,, I couldn't get the edit function to work.

[Ricky_Vato]

Well, it has been awhile since anyone has posted, but I will state this:

Bose used inferior components in the power supply and amplifier sections. The reason for the failures in a lot of units. The decision was made to used the designed parts, but cheapen on the specs and the tolerances.

According to my tech:
Bose designed the original L1 Classic and Model 1 to run on batteries as an option. Both models draw little power to operate. The Classic has two separate power supplies (one for the amps, one for the preamp), and the Model 1 has them combined on one board (cost saving and a bad idea).

The components used were the cheapest found and inconsistent quality. My tech explained that he replaced components of higher quality and by doing so, I should have no future problems with the amps or power supply. He said Bose could have used more expensive parts, but when you are selling thousands of product, you find ways to cut costs on the electronics. In other words, put in 2 cent parts that just make the specs versus spending more on longer lasting component that can withstand long term use.

So, if you do not replace the defective parts with quality ones, the Bose system will fail again. Some components are spec'd right at the limits of reliability, and can fail with heat, static, voltage spikes, ets.

I own two Classics, and one Model 1. On the Model 1, the power transistor went, blew out a weak power supply. On the Classics, the power supplies went due to poor quality diodes and resistors. My tech also replaced ICs with better quality ones.

Is it worth to repair these systems? YES. They are still very good sound systems and still look good on a stage or in any venue. The newer models have less features, and do not project in a room as the Classic and Model 1. By the way, the Classic is the BEST version as it has more acoustic power and projection than the Model 1. The model 1 has two amplifiers instead of three, but eq'd with a higher frequency bias to offset the lack of acoustic volumn the Classic has.

Right now, there is nothing new regarding sound reinforcement. I see bands, duos, solo acts going back old school for sound to save money. So to spend a couple hundred or so to repair a Bose system is worth it.