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Later 70's HH Scott

triple20

triple20

71 Cutlass S / Hurst wheels
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Just wanted to share some items I've been gathering.
A while back I decided to pick up a HH Scott 390 R,I wanted to step up into monster receiver area and I had very good service from the HH Scott 355 R I bought new in 1980 so I decided to stick with HH Scott.
After all these years the 355 R has been flawless except for 1 pot cleaning with deoxit d5.
I'm really enjoying the 390 R!
I really don't need an EQ,with the 3 tone controls and the filters on the 390 R there are over 5000 tone settings available but I like gadgets, accessories and tinkering with adjustments so I picked up the HH Scott 825 Z equalizer to go with the set up.
Just recently I scored a set of HH Scott PRO 100 B speakers. They need a good cleaning and the 15" woofers re foamed.
There's not a lot of info on these speakers but what I have found seem to speak very favorably about these speakers. Most of what I found is here in AK. Thanks for that.
I'm going to re foam them,clean and oil the cabinets,maybe re paint the black bases and go from there.Maybe I'll see about having a pro re cap the cross overs in time.
They are missing the HH Scott emblems that go on the cabinets and I doubt if I'll ever find the correct ones so in time I'll try and find some sort of HH Scott emblems to go there.
If all goes well I also have a line on a HH Scott belt drive manual turntable in really nice shape to add to my set up.
Thanks for reading me HH Scott adventure!

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That looks like a great system! Scott's were built so well. You may know already, but when refoaming that woofer, look for an appropriately "high compliance" surround. Not sure what selection you'll find at 15". They seem to be built for acoustic suspension (sealed). Putting stiffer surrounds in will lose the lower end base they were designed to provide. Worth searching hard for an appropriate replacement.
 
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Scott75s1974 said:
That looks like a great system! Scott's were built so well. You may know already, but when refoaming that woofer, look for an appropriately "high compliance" surround. Not sure what selection you'll find at 15". They seem to be built for acoustic suspension (sealed). Putting stiffer surrounds in will lose the lower end base they were designed to provide. Worth searching hard for an appropriate replacement.
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Thank you very much for the info.
What you say makes perfect sense.
I remember reading somewhere here in AK,a man said he had a job displaying these speakers at a trade show back in the day. He mentioned many people were amazed at how much movement was in the woofers when they were playing.He said many people were trying to get pictures of the movement.
Maybe I'll start a thread in the speaker section to see if anyone can make some recommendations if I don't get any here.
thanks
 
I recently acquired this R74S and got it looking good and working well. I love the clean symmetrical styling. 55 watts, and the FM tuner is great. When I got it from a recovery company, the dial glass was loose, Accessory jumpers were missing (no sound), and the selector switch was so dirty that nothing worked well. All I've done, is clean the controls, replace one burned 100 ohm resistor, repair the cosmetics, and replace the dim lamps with LEDs Debating on whether or not to do any recapping.

IMG_4879.jpeg
 
Scott75s1974 said:
Great rescue work! It's in beautiful condition. There's a long thread on r75s restoration here - much of it similar. Some helpful input from others on the bias process.
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Oh - cool. I read this thread, which was amazing and will serve as a good reference if I decide to go further in the restoration. Today, I replaced the main filter caps (just 2 in the R74S). That seemed like an easy kill. I had found something on the bias procedure, 25mV on pins 13, 15. The SM has a crazy direct current measuring procedure using an old Simpson MM (I think). I was looking replacing the old 47uF 50V caps on the driver boards, but it seems like the bottom wiring on the boards prevents them from being lifted up. Did you unwire the bottom side to service these boards?
 
I think the 74 and 75 have the same driver boards (with some different parts). Electrical connection is through square pins that come up from bottom into sockets on the top of the board. One of the electrical pins is soldered to its socket/sleave. I think it's the one closest to the middle. (see poorly drawn white circle on the image) Suck/wick out that solder and you can lift the boards out for service. (You'll need to compress the harpoon heads on the nylon board standoffs as well.) You don't need to actually unsolder the sleeve or the pin. Just get the solder out of their connection.

Edit: Actually, I don't think I used a solder sucker. What I did was compress the harpoon heads of the supports so the board was free, then I gently pulled up while applying an iron to the soldered pin/socket.
 

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Specchio said:
I recently acquired this R74S and got it looking good and working well. I love the clean symmetrical styling. 55 watts, and the FM tuner is great. When I got it from a recovery company, the dial glass was loose, Accessory jumpers were missing (no sound), and the selector switch was so dirty that nothing worked well. All I've done, is clean the controls, replace one burned 100 ohm resistor, repair the cosmetics, and replace the dim lamps with LEDs Debating on whether or not to do any recapping.

View attachment 3785523
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Very nice!
 
Oh wow, I didn't realize those were sockets, and I certainly didn't know that one pin is soldered. Thanks. This should be much easier than I thought.
 
Those daughter boards make It amazingly easy to work on. None of the other one's were soldered down on mine. I believe the PS and Preamp boards are screwed down. The tone board is soldered on with many impressively high gauge wires. None snapped on me, but I was worried. Definitely photograph that one before if you plan on changing anything.

I re-capped because mine had developed a waterfall sound at shutdown. (That's what brought me to Audiokarma in the first place.) I think it was the main filter caps, or one of the equivalents on the daughter boards. I found some, but not many caps extremely out of spec for capacitance - I don't have the ability to measure ESR.

They used high-quality parts. Ceramics are COG/NPO, most signal path resistors are carbon film.

There are some tantalum's in the drivers, pre-amp and tone boards that should be replaced. They are molded black rectangular - not the blob shaped tantalum's of later years.

I replaced the mylars with contemporary films - just because some of the mylar dipping had gaps. Probably wasn't necessary.

The PS board caps get cooked. I would definitely replace them with 105° rated ones.

On mine, they moved the decoupling caps off of the drivers and consolidated into one 1000uf under the chassis for both. That is the function of that yellow jumper. I replaced with a 1000uf on each board, had to add back a diode as well. (C3 and D1 I believe.)

The cap lists in the thread I linked above are developed in dialogue with folks here who know more than me. I recapped everything - limiting to the decoupling caps on the radio boards. It was pretty muddy sounding when I started.

It sounds beautiful now.

I've since replaced those 1/2 W carbon comp resistors on the drivers with metal film on one channel. I can not say I notice a difference. I might try replacing the differential pair with a modern, lower noise transistor and thermally couple them. But the originals are really well-matched with very low offset.

It was my grandfather's - so I did everything so I can hand it on to my children. It is one of the best looking receivers I've seen with the lid off. I have to say, the recapping with red Wima films and Green Nichicon bi-polars does give it a Sunday-car-show hood-up restored engine look.
 
Scott75s1974 said:
Those daughter boards make It amazingly easy to work on. None of the other one's were soldered down on mine. I believe the PS and Preamp boards are screwed down. The tone board is soldered on with many impressively high gauge wires. None snapped on me, but I was worried. Definitely photograph that one before if you plan on changing anything.

I re-capped because mine had developed a waterfall sound at shutdown. (That's what brought me to Audiokarma in the first place.) I think it was the main filter caps, or one of the equivalents on the daughter boards. I found some, but not many caps extremely out of spec for capacitance - I don't have the ability to measure ESR.

They used high-quality parts. Ceramics are COG/NPO, most signal path resistors are carbon film.

There are some tantalum's in the drivers, pre-amp and tone boards that should be replaced. They are molded black rectangular - not the blob shaped tantalum's of later years.

I replaced the mylars with contemporary films - just because some of the mylar dipping had gaps. Probably wasn't necessary.

The PS board caps get cooked. I would definitely replace them with 105° rated ones.

On mine, they moved the decoupling caps off of the drivers and consolidated into one 1000uf under the chassis for both. That is the function of that yellow jumper. I replaced with a 1000uf on each board, had to add back a diode as well. (C3 and D1 I believe.)

The cap lists in the thread I linked above are developed in dialogue with folks here who know more than me. I recapped everything - limiting to the decoupling caps on the radio boards. It was pretty muddy sounding when I started.

It sounds beautiful now.

I've since replaced those 1/2 W carbon comp resistors on the drivers with metal film on one channel. I can not say I notice a difference. I might try replacing the differential pair with a modern, lower noise transistor and thermally couple them. But the originals are really well-matched with very low offset.

It was my grandfather's - so I did everything so I can hand it on to my children. It is one of the best looking receivers I've seen with the lid off. I have to say, the recapping with red Wima films and Green Nichicon bi-polars does give it a Sunday-car-show hood-up restored engine look.
Click to expand...
Thanks for all this specific R7xS experience. I totally understand wanting yours to last another generation. The one I have was an add-on to a Marantz 2215B purchase, but now I really like it more. It has something extra in the styling, and the quality is there.
 
Thanks for the help on removing the driver board. Now ready to replace some caps, as shown in the photo. May need to extend the lead(s) on the C2 replacement. I would populate C3 and D1 and remove the 1000uF under the chasis, but I don't really have a full understanding of what to do. Any advice?

IMG_4925.jpeg
 
OK I figured out that once you remove the jumper from the C3 positive lead, the connection to the chasis mounted 1000uF cap is removed. Installed C3 1000uF caps on each driver board along with a 1N4007 D1. Then removed the old 1000uF Chasis mounted cap and jumper between channels. Set bias to 25mV on pin 13-15 each channel. Now testing. May tackle the preamp board next.

IMG_4930.jpeg
 
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