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Stewart 1400-PA

P

ptmbass

May 22, 2020
10
0
#1
Need sound advice...
Stewart 1400-PA, prob25 yrs old.
Used on live kybd gigs for couple of yrs.,
Remainder til last week powering a pair of Tanonoy for 20 yrs.in smoke free project studio.
Right side all of a sudden got soft, distorted low at his volume.
Then zip.
So...is it worth sinking $ into a 25 yr. amp that cost nearly $1000 back in the day or just replace?....don't need all that power anyway.
Thnx!
Mark
 
Last edited:
#2
ptmbass said:
Need sound advice...
Stewart 1400-PA, prob25 yrs old.
Used on live kybd gigs for couple of yrs.,
Remainder til last week powering a pair of Tanonoy for 20 yrs.
Right side all of a sudden got soft, distorted low at his volume.
Then zip.
So...is it worth sinking $ into a 25 yr. amp that cost nearly $1000 back in the day or just replace?....don't need all that power anyway.
Thnx!
Mark
Click to expand...

Not worth repairing IMHO.

Here's a used one for $140. [Invalid or Expired Link Removed]


You can buy a brand new quality power amp for pretty reasonable money, especially if you don't need monster power.

People seem to like these well enough: Crown XLS 1002

If you scroll about 1/3 down the XLS 1002 product page, there is a power matrix that shows the power level of the entire XLS product line.
 
#3
Thnx....amp was literally on 24/7 [not counting the usual power outtages]
Sorta what I figured.
I got a replacement from my bro'>Crown PB1 1/3 the power, much bigger/heavier but only about 15 hrs usage!
Been sitting unused in his garage for the last 15-20 yrs.
So I'm set as it was free....but it breaks my heart to have to dump a $ss high end amp.
I read and was told leaving amps on w/no signal was less stressful and better for amp than off/on every day.
Wasnex said:
Not worth repairing IMHO.

Here's a used one for $140. [Invalid or Expired Link Removed]


You can buy a brand new quality power amp for pretty reasonable money, especially if you don't need monster power.

People seem to like these well enough: Crown XLS 1002

If you scroll about 1/3 down the XLS 1002 product page, there is a power matrix that shows the power level of the entire XLS product line.
Click to expand...
 
#4
ptmbass said:
Thnx....amp was literally on 24/7 [not counting the usual power outtages]

I read and was told leaving amps on w/no signal was less stressful and better for amp than off/on every day.
Click to expand...
Not necessarily true. Continuous hours and number of power-ups both factor into the aging of the amp.
 
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#5
agedhorse said:
Not necessarily true. Continuous hours and number of power-ups both factor into the aging of the amp.
Click to expand...
The ambient temperature when the amp is operating can make a huge difference in longevity, too. I've seen amps in permanent installs in hospital comm rooms that are air conditioned, and the amps last and last.

Conversely, I've worked on banks of emergency paging amps racked up in a coal fired power generating plant, where someone decided it would be smart to install them on the 3rd level in the generating hall where ambient temperatures reach 115F, not to mention the coal dust. These amps didn't lead a very long life.
 
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#7
The ave. temp in the AC/summer, baseboard heat/winter studio was always around 70-74*

byacey said:
The ambient temperature when the amp is operating can make a huge difference in longevity, too. I've seen amps in permanent installs in hospital comm rooms that are air conditioned, and the amps last and last.

Conversely, I've worked on banks of emergency paging amps racked up in a coal fired power generating plant, where someone decided it would be smart to install them on the 3rd level in the generating hall where ambient temperatures reach 115F, not to mention the coal dust. These amps didn't lead a very long life.
Click to expand...
 
#10
Of course that makes sense....
The Stewart is fan cooled,,,1 fan>right thru the middle front to back....
Not sure if the fan is conrolled by a thermostat....or the fan failed.... as it doesn't go on today when I plug it in[temp. controlled bt themostat?]
If the fan failed, since it was real quiet the I first bought it, I wouldn't have caught that and could've possibly overheated[?]
 
#11
ptmbass said:
Of course that makes sense....
The Stewart is fan cooled,,,1 fan>right thru the middle front to back....
Not sure if the fan is conrolled by a thermostat....or the fan failed.... as it doesn't go on today when I plug it in[temp. controlled bt themostat?]
If the fan failed, since it was real quiet the I first bought it, I wouldn't have caught that and could've possibly overheated[?]
Click to expand...

If the fan has been running continuously for over a decade there is a good chance the fan and cooling corridors inside the amp are clogged with dust and other nasty stuff.

I have three QSC PL236s that were pulled from a permanent install. The insides were filled with oily, linty sludge that was restricting air flow and smelled pretty nasty.

I sent them to an authorized QSC repair center for cleaning and repair. Two of the amps function normally except they make a really loud pop when they are turned off. The tech said the boards showed thermal damage and would not hold a repair. He said the circuit cards were falling apart when he dipped the soldering iron into the board to remove components.

My daughter also used to chide me for turning off my computer at night, using the same logic. But twice a year I had to open it up and pull lint and cat hair off the video card fan.

The other thing to consider is from time to time the electricity goes off and on and this can put a pretty significant transient on the line that can stress to components.

IMHO, if you not using it for an extended time, turn it off. If your going to leave it running continuously, you need to occasionally have the cooling system serviced.
 
#16
Wasnex said:
The other question would be if the amp is actually repairable. Parts may be obsolete and unavailable.
Click to expand...
I 've already emailed Stewart and they told me they don't repair this model anymore ...so i guess that answers the question>obsolete/unavailable parts. If they won't repair it....well then.
Which I guess I woulda found out from any svs.tech I would take it to after they opened it . assessed and then charge me for the diagnostic....
Do reputable techs research 1st to see if they can get parts before they put it on the bench?
 
#18
I appreciate your attachment to it, but it's 20+ years old, the fan has been off for an indeterminate length of time while the amp was on quite probably leaving it wide open for thermal-induced problems, and Stewart themselves have orphaned it.

It's time to move on.

Power amps have become remarkably cheaper with offshore production and the move to powered cabinets both for touring sound, and for us guys that play VFW's and those places your mama warned you about. Cheaper than they've ever been for big power, and you could find barely used amps if you look carefully and the prices on them are falling as well.
 
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#19
ptmbass said:
I 've already emailed Stewart and they told me they don't repair this model anymore ...so i guess that answers the question>obsolete/unavailable parts. If they won't repair it....well then.
Which I guess I woulda found out from any svs.tech I would take it to after they opened it . assessed and then charge me for the diagnostic....
Do reputable techs research 1st to see if they can get parts before they put it on the bench?
Click to expand...

I doubt it. I am sure most would tell you if they knew off the top of their head, but you can't expect a tech to research every component in an amp before they put it on the bench.

I have some old GK 2000RB amps. I started with one that looked really nice but has been a real lemon. When I bought it, one output section was intermittent and the fan didn't want to come on. The first problem was caused by a flaky fuse. While trouble shooting the fan, I accidentally brushed a component with a test probe and caused a major melt down in the output section. Blown drivers, blown diodes, blown resistors, blown output devices. I did some troubleshooting and then starting researching the needed semiconductors. Turns out the outputs and drivers are obsolete. I found one source, but the minimum purchase was 50 each. This may have been a blessing in disguise since there was so much damage spread throughout the circuit.

I wound up buying a beater 2000RB for a working output card. I was listed as fully working but only one of the outputs was good. The amp was really rough cosmetically and the insides were drenched in hazer fluid.

I had to perform a few factory updates on the good output card in the original amp to get it to sound like the card I cannibalized from the basket case. Eventually I also had problems with the I/O board and preamp in the original amp, so I have cannibalized those as well. Sometimes that's the way it goes with an old amp.
 
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