HH Scott 399 w/ Type 335 FM Stereo Multiplexer

SCompRacer

Next up on the bench, an HH Scott 399 with HH Scott Type 335 Stereo Multiplexer.

The Scott 399 was produced in '59-'60, just before FM multiplex stereo broadcasts were initiated in 1961. The receiver sported separate AM and FM tuners for the short-lived simulcast mode. FM received the left channel and AM the right.

Scott produced the Type 335 FM Stereo Multiplexer so you could enjoy true stereo FM without investing in a new receiver.

The 399 has a fully integrated power amplifier with four 7189 output tubes and it includes a phono stage.

mhardy6647

Great stuff - from Powder Mill Road in Maynard, MA.
Gorgeous, too. The aesthetics of Scott's round dial tuners (and the considerably rarer, even here in New England) receivers are unassailable.
I am (indeed, I remain) envious.

xschop

Lovely.

pitdogg2

Those 7189 tubes have escalated in price in the last few years. I got some good deals on a few of them about 7 years ago not so much anymore. Do not know if that can take the 7189a tube. As I understand it the pinout is different on the 7189a vs 7189. Technically speaking pin 1 and pin 6

SCompRacer

mhardy6647 wrote: »

Great stuff - from Powder Mill Road in Maynard, MA.
Gorgeous, too. The aesthetics of Scott's round dial tuners (and the considerably rarer, even here in New England) receivers are unassailable.
I am (indeed, I remain) envious.

The owner has good taste! I am shocked as you typically have at least of one of everything!

It’s rare to find a Scott without a visibly cracked tuner dial. Plastic hub with a set screw, what could go wrong? I may do the ‘two loops of 22-gauge tinned hook up wire wrap around the dial hub’ like I did with the 340.

xschop wrote: »

Lovely.

They sure are and they sound great too.

pitdogg2 wrote: »

Those 7189 tubes have escalated in price in the last few years. I got some good deals on a few of them about 7 years ago not so much anymore. Do not know if that can take the 7189a tube. As I understand it the pinout is different on the 7189a vs 7189. Technically speaking pin 1 and pin 6

Like with many tubes, the prices are up there! Kazakhstan and Ukraine have some deals…but are too risky for me. There is a Quad of NIB NOS Mullard in Vietnam for $717 with free shipping!

On 7189, pin 1 and 6 are not used. On 7189A, pin 1 & 2 and 6 & 9 are connected so you have to check if the manufacturer hasn’t used the unused socket pins as tie points for other wiring. If they are, you can mount a terminal strip and move them. (Loose free air connections are not a good practice in point to point). 6P14EB is another choice.

An example of using unused socket pins is found on the Scott 340 7591 tube. Pin 1 is not used. (Depending on branding, you may have a pin 1 in base or not). They tied a big old resistor across in series with two wires on the pin 1 sockets of two 7591 output tubes. Saved them from mounting a terminal strip.

mhardy6647

7189(A) -- I'll tell ya what, those Rooskie 6П14П-ЕВ 6P14P-EV tubes serve well and sound good in my (albeit somewhat limited) experience.

I put a quad of them into a Realistic SAF-40 (which is known to immolate a normal 6BQ5, even though R/S never, AFAIK, specified that it should be used only with 7189s) and they worked a treat.
Back then (two-ish decades ago), the 6P14P-EV tubes were cheap. Probably not no mo', tho'.

PS The pin 1 observation's a good one.

The unsuffixed 7189:



The 7189A:






EDIT: A concise synopsis (yeah... that's redundant, isn't it?)

https://www.bustedgear.com/res_Tube_7189.htm

pitdogg2

They didn't call them 6 BBQ 5's for nothing

SCompRacer

mhardy6647 wrote: »

EDIT: A concise synopsis (yeah... that's redundant, isn't it?)

https://www.bustedgear.com/res_Tube_7189.htm

They say trust, like love, needs to be reaffirmed from time to time...

The 340 had three Scott branded Westinghouse manufacture 7591 tubes in it and one oddball wiped clean. One Scott tube was visibly bad, white top. I got two from Carl, a Westinghouse and a Lowery and I'm betting Westinghouse made it. They have no pin 1. The Scott does.

I could see a lead coming from pin 1 on the Scott tube that is attached to something in tube, so I removed the glass. No continuity. Further destruction would be required to see what goes on in the base. That resistor across the pin 1 sockets is factory as I've seen it on other bare nekkid 340's.

It tells me make absolutely sure before sticking anything in the socket other than what it was spec'd for...

SCompRacer

Today I tested 23 tubes for the 335 and the 399. Only one bad 6U8 in the 399 which is a good thing. Two are 6F66/EM84 magic eye tubes for the tuners. I'll do those in circuit. There were multiple sentences of jump this and resistor across that to bother.

Three tubes were broken in shipping due to bad packing by the seller who failed/refused to remove the tubes. Two 7189 and a GZ34. Bubble wrap around a 44-pound object, even double boxed, is not good packing. It's a wonder more damage wasn't incurred. Fortunately, the tuner and all controls operate smoothly. I had to reglue some joints on the cabinet.

The wife gets on me today saying I used to be so neat and organized. I leave tools out on the bench. Test leads hanging. I would have made a form for the tube list. Now I'm just retired and lazy, I guess. I say what's the big deal, I can read my writing.

I got ahead of myself and cleaned the cabinets up.

A tube pin straightener is a must have.

mhardy6647

The MPX's enclosure in particular is (now) beautiful.

Yes. Tube straighteners. I have my father's (one of those once-ubiquitous 7 pin/9 pin dealies with Red and Blue plastic 'trim'). I also have another, identical one that I picked up... somewhere or another, at some time or another.

SCompRacer

This could be a Monday morning chassis. They punched a can capacitor hole in the wrong place and patched it. Might be a press fit with a couple rivets at edges for insurance. You don't want it popping into chassis when you plug a tube in.

Both tuner dial hubs were cracked so I did the superglue, two wire hub wrap and coat of epoxy fix.

Foam under magic eye bezels was dried out. I cut some out of a larger piece and used double sided tape to attach to chassis front.

pitdogg2

I've been looking for one of those metal 7/9 pin straighteners for a looong time. They are hard to come by I'm finding.

mhardy6647

re: the chassis gaffe. Youch!

SCompRacer

Upay, I mean, ebay has some pin straightener offerings. I got that one off ebay a long time ago. Didn't cost much as I recall.

pitdogg2

SCompRacer wrote: »

Upay, I mean, ebay has some offerings.

I've seen plastic, I've must have missed the aluminum or steel models OR they were way more than I'm willing to pay 😉 you've seen me in person you know what a cheap ************ I am 😄

SCompRacer

We prefer the word thrifty.... They have a multi one for thirty ducks.

SCompRacer

The chassis mount antenna was broken and had seen some previous repair attempts. It was cracked too badly to attempt another epoxy fix. The heat from the GZ34 didn't help condition of plastic.

I cut a chunk off a sheet of plastic. Clamped it in a folding work bench. A heat gun was used to get it pliable, and a handy nearby file helped bend it to desired angle very close to original design.

Edges were filed, corners rounded, drilled some holes and nut and #4-40'd it together. Next trip to hardware store I'll pick up some aluminum rivets.

mhardy6647

The mount failure rate of rod antennae on old receivers especially (i.e., as opposed to old tuners) is close to 100%, I think.
The later Scott ss receivers had a sticker that said not to use as a handle -- but I think that the great unwashed was just too, too tempted.

SCompRacer

This Miller 705-A sure looks like a handle....lol

pitdogg2

My Sansui 719 tuner has that very sticker on it's AM antenna

SCompRacer

I'd better get the P-touch out and print a warning.....I resisted the urge to use dumb a**.

SCompRacer

I've been finding too many things wrong to attempt powering the 399 up with variac/dim bulb. Some are capacitor related. I started replacing those today. Still waiting on the Adapt a caps for the remaining six cans. C1 is the most difficult and I'm stuffing that can as it is at the very rear of receiver. You gotta make sure the right value is attached by the correct symbol.

I have this Candohm resistor, R182 A, B, C in the schematic. It is supposed to be three 250-ohm in series, or 250, 500 and 750. This one measures 394.6-ohms across the first one and 1.178K-ohm total. I was surprised to see a reading, while high, to ground with it. I googled and learned the cambric paper burns thru and they can eventually short to ground.

SeleniumFalcon

This is a great thread, Rich!

SIHAB

Yes, thanks for the thread!

I get a headache looking at one line drawings...
I wish I had the patience.

SCompRacer

Thanks for the kind words! Oh I get headaches...lol

There is not much info on 399 repairs in the forums. Xraytonyb on youtube has a six-part video repairing a 399. (Link below). He had one that was really messed up. He touched upon many issues in the 399 which made it easier for me. He also pointed out errors in schematic/parts list with missing decimal point for resistors, so best to verify old parts before ordering anything directly off schematic/parts list. Love his $2,500 scope too!

https://www.youtube.com/watch?v=qhLVFJ6gR4Y

First, some progress. A terminal strip and three wire wound 250-ohm 5 watt 1% resistors replaced the Candohm. They are mounted favoring the side of chassis so they don't melt wires. (I have the wiring to front panel pulled aside to snap picture). Now we have 250/500/750 ohms. Wiring to be added when I do C8 capacitors.



One thing I haven't seen anyone do is remove the resistor farm in middle of chassis. Two #6 sheet metal screws secure it. Lots of wires that connect to and go through it. That 'farm' obscures some rivets for the can mounting wafers. I also want to replace the selenium rectifier, something xraytonyb did not do.





Now we're in really deep.....

I want to drill a new hole for a bridge rectifier as the holes for the selenium strap are quite large for a 6-32 screw. I also want to move it over so I can make room for a chassis mount 33-ohm resistor. Currently, a 33-ohm 5-watt resistor cooks the carbon resistors above it. Carbon resistors can change value when heated. The bias resistor is at very top so a metal film will replace the carbon.



One issue that is all mine, resistor R172. This is the first step down resistor in B+ off the GZ34 (380vdc to 360vdc). The schematic, Tony's 399 and one other fellow had a 160-ohm resistor in that location. I have a 120-ohm. It looks factory or we had a real good tech that replaced it. I'll be adding a 40-ohm in series to correct value to 160-ohms before powering up. I can always remove it. It will be replaced with a chassis mount.



Space to rent now! If I can't figure out where all the wires go, I'll be heading east to a couple guys houses.....



160-ohm 2W? 15K to ground, yeah, chassis mount for you too along with the 2K-ohm.

schwarcw

Lookin' good Richee!

SCompRacer

Thanks Carl!

Some progress. The selenium rectifier has been replaced with a BR34 diode bridge. The 33-ohm cement resistor that was hugging the carbon above it was replaced with 33-ohm 15-watt chassis mount. Holes in resistor mounting were perfect for a 4-40 tap so no nuts needed. I had to mount it a little crooked. The first mounting point had to be between resistors (that measure good) on opposite side. Had to drill second mounting hole above existing large hole.


Yeah, it was a second attempt as the first one was too close to terminal strip.


Adapt a cap mounting boards are here.

SCompRacer

Why Adapt a cap? If you have room in the chassis, you can also mount caps on terminal strips. I was able to do that for two cans in the Scott 340. The 399 is a tight chassis, not much room.

If you have the budget, you can purchase newly manufactured can capacitors made by CE Manufacturing. The Scott 399 has seven can capacitors. Two are common positive which CE does not make (and CE does not manufacture custom values). So, five cans times average of $50 = $250 plus shipping. Hayseed Hamfest will make common positive cans so add another $82 plus shipping or $332.

Hayseed Hamfest in the UK installs modern capacitors into new cans. They sell kits for popular audio gear or will provide a quote for you. They will custom make cans to your values. They average ~$41 each x 7 = $281 plus shipping.

You can disassemble old cans and stuff them with new caps but it’s time consuming, messy and can be smelly. You have to salvage parts like the wafer with terminals or you make a new one.

Adapt a cap are a high-quality part that makes this recapping job easier. They mount in place of the typical size can capacitors. A five pack costs $25, 10 pack $40 and 20 pack $65. I purchased a 10 pack and have $75 in good quality Nichicon UCY capacitors, so we are at $115 plus shipping. We also have film caps, resistors and tubes to purchase as well.

Adapt a cap assumes you know what to do with them as there are no instructions included. There are no technical specs listed on their web site either, like voltage/amperage. Folks have successfully used and do like them.

The Adapt a caps match the symbol order on the bottom of can capacitors; no symbol, half round, square and triangle. Although the symbols are rather small, I could see them all. (Yeah, that song got stuck in my head today).

The side marked frame is considered chassis side. If you flip it over, the symbols are reversed. No big deal as long as you connect wires to the correct uf value terminal, if they will reach. With point to point, sometimes there is no extra length in wires. I drew diagrams and took pics of connections, so I prefer to mount the adapt a caps like the can was installed.



I install the capacitors from this side, opposite the frame side. Symbols are there to guide you.



Can capacitors ground through the mounting tabs. They can attach directly to a metal chassis and ground, or mount on an insulating phenolic wafer like Scott did. A ground wire is then attached to the can mounting tabs. As supplied, the negative leads of the Adapt a caps are not connected to the chassis ground contact points. This is a great option if you have to make a common positive can. If you want the negative leads to contact ground at mounting points, add a jumper between - and frame.



I start in a clean area. I write down the capacitor number in the circuit, uf/voltage values and symbols. I write the replacement value next to it. (If exact value uf/voltage not available, you install a larger value). I grab only the values I need, test and install them.



Ideally, they fit four 12.5mm caps with 5mm lead spacing. (Modern caps of typical values needed are small). Widest spacing you could use before bending leads, 7.5mm. If you used larger capacitors, like 16mm, you’d have to bend leads slightly. Larger caps would have to be staggered/stacked and leads extended, just like folks do when stuffing cans.

This is a common positive, so leads must be reversed.



I don’t know if there is some standard for how the two mounting holes are drilled in relation to the can symbol order. Where Scott drilled the holes, some of the adapt a caps ended up being turned 90 degrees counterclockwise. The picture shows how the can was mounted and how the Adapt a cap compares. I'll have to turn my picture and drawing to match.



One issue with the Adapt a caps are no terminals. The 399 chassis is pretty tight, and some terminals have resistors to ground, capacitors or multiple wires. I found a 12-gauge wire fits in the larger ground and supply holes so I could add terminals. Then I realized I could flatten a 12-gauge wire and drill a small hole in the flat and eliminate the terminal.




On simple one wire connections, I folded lead down to contact board and made a U to hook other wire on. Flatten, squeeze with needle nose and solder.



Having terminals raises connections and makes it easier for me. When I run out of cable spaghetti, I cut a length of wire and start pulling the strands out and slip it over the solid hookup wire.



I had two in chassis cans that used a grounding mount riveted to chassis. I removed the clamps and mounted these on stand offs. You can see I jumped the - to frame so they would ground to chassis.



This is what it looks like from the top. I stuffed the can at rear as it was in an unprotected area. One could remove innards from cans and attach the empty cans over the caps. A couple dabs of silicone or tar to hold them... We are close to a variac/dim bulb power up.

schwarcw

Damn that's some fine work to populate those small boards. Fire that mother up!

pitdogg2

Hey Carl! How you doing pal?

SCompRacer

Hey Carl! Fire extinguisher is close by!

Replaced ceramic resistors with chassis mount. Mounting hole size for all three were good for 6-32 tap. I installed the called for 160-ohm in place of the 120-ohm I found in its place and was happy I did. One terminal strip was pretty cooked so removed it, connected wires direct between 160 and 2K ohm. The third resistor is 15k-ohm to ground so that side of chassis gets warm instead of ceramics baking wires/components above it.



It passed the variac/dim bulb power up to line voltage without high amperage, smoke and fire drama. I couldn't get past 100vac before, so now I could remove the dim bulb and can run up to line voltage briefly to test voltages. The variac is still helpful as you can reduce voltage while you make sure tube bias isn't excessive. We are at 122.5vac today. Kill a watt shows it pulling 1.19A. The 399 fuse is 2.5A.

Negative bias voltage came in at -53.95, schematic calls for -55vdc. B+ spec is 380vdc at line voltage of 117vac from GZ34 before the 160-ohm step down. I get 421vdc at 122vac line so I'm within that 15% +-. (437vdc would be15% over).

Check out what 117vac does with B+. 405vdc, -16vdc lower. Thats why some guys use bucking transformers or thermistors to reduce line voltage on their vintage gear. Thermistors must have amp rating for the gear it's installed in and I read they can drop 2vac. I guess the main thing is if you can bias tubes properly at your line voltage. Xraytonyb changed a resistor (8.2k to 10k) in the bias circuit of his 399 to allow more adjustment from the pot.

Bad news, missing B+ in a circuit. FM doesn't work, played vinyl but volume and balance pots need work.





B+ at line voltage of 122vac.

B+ at line voltage of 117vac.