Nice find. That faceplate looks almost perfect! I see a small amount of wear on the dial glass edging around the tuning knob and meters, but that is probably just from normal usage. Are you planning a full cosmetic and electrical restoration?
He just dropped it off and it sounds pretty darn good. It does need some cleaning. 409 and Restor-A-Finish can take care of it. I will have to check the bias and see if anything looks dodgy or it's had any previous work done. The volume knob is a little loose, so the faceplate will have to come off at some point to fix that.
I picked up an oddball yesterday - it's a Montgomery Wards Model 450. Turns out Harman Kardon built this and at least one other model for Wards. This has the same output board as the HK 730 and one of their integrated amps. The guy I bought it from had "some work done on it" - that work turns out to be the entire power amp section was rebuilt by a tech in the Quad Cities. I'll rebuild the preamp/tone board this winter. It's a keeper!
Nice find. Looks very clean. And good detective work in tracking down some service data. Sometimes the most difficult part of servicing old gear is tracking down a readable schematic. (I have an old Realistic STA45B FM Stereo Receiver that needs work. I've been trying to track down a schematic for years. No luck so far.)
This is my Hafler DH500 amp. It's about 35 years old and I had the electrolytic caps replaced along with the bias and offset pots 6 years ago. It weighs 45 pounds.
I'm not Ron but I've had Hafler's for about 35 years and still own a 220 that easily powers any 4 ohm load I've thrown at it. I've also done the same mods Ron listed and did a complete rebuild on an XL280 with Musical Concepts boards, caps and dual power supplies.
I've known a DH200 to be 4 ohm stable, but never saw the actual spec sheet like above. I know back then 8 ohms were normal, and speakers were in general more sensitive too. I was just curious..
From the internets: "In 1981 the audio magazine Stereo Review bench-tested one for an article and recorded it clipping at 434 watts into 8 ohms. Dynamic output was 792 watts into 4 ohms and 653 watts into 2 ohms. Not too shabby!"
I ran a pair of 2 ohm ribbons with it for years. They were fused with a 3 amp fuse so the amp never got close to full output. I found a few references over the years that said you could weld with it.
Ron, nice unit. Now you have to pop the cover and show us the big engine! I think this one has a big heat sink tunnel type config with a fan on one end, like the Ampzillas, right? I'd imagine that with a 2 ohm load, the fan would kick up to high speed to keep the outputs cool? Or maybe the fan stays off most of the time.
The fan is always on but at idle it is very quiet as in put your ear next to the amp to hear it quiet. It was always outside the listening room when I drove the 2 ohm load and I doubt that it ever ran hard enough to kick the fan speed up. The ribbons were 91db/1w in an active system so it didn't take much to get them loud.
@Wolf said:
I've known a DH200 to be 4 ohm stable, but never saw the actual spec sheet like above. I know back then 8 ohms were normal, and speakers were in general more sensitive too. I was just curious..
Sorry Wolf, I fat-fingered the previous post. It's a 220 rather than a 120. Sorry about that!
I've never thought to leave an amp on all the time. Does it pull much current at idle? I know many people leave all their gear on 24/7 and pro amps in many installs stay powered up for decades.
Not exactly a piece of hifi gear but our paging amp at work had been on continously for the 10 years I've worked there and I don't know how many more years before I started there. It looks like it's from the early/mid 2000's and is class AB. Put my hand on it once and it wasn't even warm to the touch. Makes sense. I had a professor tell us that heat cycles and inrush currents are what's hardest on electronic components.
When I started at the TV station in '85 there were racks of old B&W tube monitors, test equipment, and video & RF gear that had been running continuously for decades. The racks were built into a long wall in master control and the room behind them had AC pumped in & aimed right at the racks. I was told they rarely needed any maintenance because they were never power cycled and kept nice and cool. I do remember always bringing a sweatshirt with me even in the Summer because they kept it so cold in there.
Yeah, that amp is in our IT room with all the IT servers and it has a dedicated mini-split AC unit that keeps the room at a constant 70F. It's also on a UPS that is fed by our 45Kw backup generator. Livin the good life
@6thplanet said:
Yeah, in rush current and power cycling is why I just leave it on. It's a little warm sitting there.
In addition to what has been said above, I've also read that high humidity is also a destroyer of electronics and circuit boards. Like storing a piece of equipment in a cold and humid basement is not a good idea. So if you leave a piece of equipment on 24/7 and it gets slightly warm, this lowers the relative humidity in the immediate vicinity around the circuit boards.
@4thtry said:
So if you leave a piece of equipment on 24/7 and it gets slightly warm, this lowers the relative humidity in the immediate vicinity around the circuit boards.
I never even thought of that. We played some pretty dark, damp dives back in the day, but didn't dare leave the power distro connected if it was a 2 nighter.
I would hope they could design a better speaker, considering all the advances in the software over the past 20 years. It does make my brain hurt to see the mid & tweeter mounted side by side like that.
Comments
Wow, very nice.
Nice find. That faceplate looks almost perfect! I see a small amount of wear on the dial glass edging around the tuning knob and meters, but that is probably just from normal usage. Are you planning a full cosmetic and electrical restoration?
He just dropped it off and it sounds pretty darn good. It does need some cleaning. 409 and Restor-A-Finish can take care of it. I will have to check the bias and see if anything looks dodgy or it's had any previous work done. The volume knob is a little loose, so the faceplate will have to come off at some point to fix that.
Sweet acquisition, Tom!
I picked up an oddball yesterday - it's a Montgomery Wards Model 450. Turns out Harman Kardon built this and at least one other model for Wards. This has the same output board as the HK 730 and one of their integrated amps. The guy I bought it from had "some work done on it" - that work turns out to be the entire power amp section was rebuilt by a tech in the Quad Cities. I'll rebuild the preamp/tone board this winter. It's a keeper!
Nice find. Looks very clean. And good detective work in tracking down some service data. Sometimes the most difficult part of servicing old gear is tracking down a readable schematic. (I have an old Realistic STA45B FM Stereo Receiver that needs work. I've been trying to track down a schematic for years. No luck so far.)
Good luck with the project.
This is my Hafler DH500 amp. It's about 35 years old and I had the electrolytic caps replaced along with the bias and offset pots 6 years ago. It weighs 45 pounds.
Ron
Very nice !
That's the real deal!
But is it 4 ohm stable, Ron?
InDIYana Event Website
I'm not Ron but I've had Hafler's for about 35 years and still own a 220 that easily powers any 4 ohm load I've thrown at it. I've also done the same mods Ron listed and did a complete rebuild on an XL280 with Musical Concepts boards, caps and dual power supplies.
I still highly covet Hafler amps.
I've known a DH200 to be 4 ohm stable, but never saw the actual spec sheet like above. I know back then 8 ohms were normal, and speakers were in general more sensitive too. I was just curious..
InDIYana Event Website
That's a beauty, Ron! I've always wanted a big Hafler, but never found one locally that was in such pristine condition.
From the internets: "In 1981 the audio magazine Stereo Review bench-tested one for an article and recorded it clipping at 434 watts into 8 ohms. Dynamic output was 792 watts into 4 ohms and 653 watts into 2 ohms. Not too shabby!"
I ran a pair of 2 ohm ribbons with it for years. They were fused with a 3 amp fuse so the amp never got close to full output. I found a few references over the years that said you could weld with it.
Ron
Ron, nice unit. Now you have to pop the cover and show us the big engine! I think this one has a big heat sink tunnel type config with a fan on one end, like the Ampzillas, right? I'd imagine that with a 2 ohm load, the fan would kick up to high speed to keep the outputs cool? Or maybe the fan stays off most of the time.
I found this picture on the web.
The fan is always on but at idle it is very quiet as in put your ear next to the amp to hear it quiet. It was always outside the listening room when I drove the 2 ohm load and I doubt that it ever ran hard enough to kick the fan speed up. The ribbons were 91db/1w in an active system so it didn't take much to get them loud.
Ron
Sorry Wolf, I fat-fingered the previous post. It's a 220 rather than a 120. Sorry about that!
Jim
My DH200 is still going strong since the overhaul in 2020. It only gets shut off when I leave for vacation.
https://diy.midwestaudio.club/discussion/1484/hafler-dh200#latest
I've never thought to leave an amp on all the time. Does it pull much current at idle? I know many people leave all their gear on 24/7 and pro amps in many installs stay powered up for decades.
I leave the dreadnaught on and probably shouldn't. It's biased pretty high into Class A and just sits there and heats the space.
Not exactly a piece of hifi gear but our paging amp at work had been on continously for the 10 years I've worked there and I don't know how many more years before I started there. It looks like it's from the early/mid 2000's and is class AB. Put my hand on it once and it wasn't even warm to the touch. Makes sense. I had a professor tell us that heat cycles and inrush currents are what's hardest on electronic components.
When I started at the TV station in '85 there were racks of old B&W tube monitors, test equipment, and video & RF gear that had been running continuously for decades. The racks were built into a long wall in master control and the room behind them had AC pumped in & aimed right at the racks. I was told they rarely needed any maintenance because they were never power cycled and kept nice and cool. I do remember always bringing a sweatshirt with me even in the Summer because they kept it so cold in there.
Yeah, that amp is in our IT room with all the IT servers and it has a dedicated mini-split AC unit that keeps the room at a constant 70F. It's also on a UPS that is fed by our 45Kw backup generator. Livin the good life
Yeah, in rush current and power cycling is why I just leave it on. It's a little warm sitting there.
In addition to what has been said above, I've also read that high humidity is also a destroyer of electronics and circuit boards. Like storing a piece of equipment in a cold and humid basement is not a good idea. So if you leave a piece of equipment on 24/7 and it gets slightly warm, this lowers the relative humidity in the immediate vicinity around the circuit boards.
That is true Bill.
I never even thought of that. We played some pretty dark, damp dives back in the day, but didn't dare leave the power distro connected if it was a 2 nighter.
The vintage guys may be awakening to modern drivers and materials. (And they've begun selling Wharfdale.)
My parents have a pair of L710 that they bought when I was a kid that still look and sound great.
I would hope they could design a better speaker, considering all the advances in the software over the past 20 years. It does make my brain hurt to see the mid & tweeter mounted side by side like that.