Realistic SAF-40B service manual or schematic needed

[bfreemannh]

Hi Folks,
My uncle gave me a Realistic SAF-40B stereo tube amplifier. This will be my first tube repair.
It is not making any sound, not even a scratch or pop. I can see that all the taller GE Electronic 188-5 tubes are lit up, but I do not see any light from all the smaller tubes. I figure a good place to start is by checking the voltages but I am unable to find a service manual or schematics for this unit. Maybe a schematic from a SAF-40 or a -40C would be close enough to get the job done.

Any help would be much appreciated. Thank you!!

 

[Tom Bavis]

What I find in the Sams index is SAF24, Stereo 40A / Stereodyne 40. Dunno how close any of these might be... post a picture.

 

[bfreemannh]

Here is a couple of pics. let me know if you need any more info.

 

[FMB42]

Have you cleaned the control pots and switches?

Did you power it up on a dim-bulb or variac?

 

[s-petersen]

The center small tube in front looks like it lost it's vacuum, can you take it out and post a pic of it?

 

[gadget73]

yeah, the milky one does look to have gone to air.

The 188-5 code is actually the GE production numbers. 188 is GE's EIA code, and I think the -5 means it was made in their Owensboro, Kentucky plant. There will be another number etched on the side someplace, probably 6BQ5.

The small tubes look like they might be Matsushita tubes.

From experience with other similar-vintage Japanese tube gear, I'll toss in the suggestion to replace the caps. The Japanese ones from this time period seem to be especially terrible, and they will cause the output tubes to self-destruct if they get leaky.

 

[bfreemannh]

I brought it up on a viriac with a visual on current. It's not shorted or drawing much.
I only cleaned the tube pins and found no visual defects under chassis. I have no tube experience and did not jump to a conclusion based on the looks of the tubes. I will agree that it has lost all it's top silver coating, compared to the others. Since I had no output at all, I did not feel the need to jump right on cleaning the pots. My initial thoughts were to check voltages before tearng into it.
If this tube has lost it's vacuum, would this result in no output at all?

 

[gadget73]

Depending what its used for, maybe. Or maybe only loss on one channel. Or maybe just certain functions wouldn't work.

What sort of current draw are you getting? It should likely be no more than an amp, but probably more than a half amp.

Is the big octal tube glowing? Thats your high voltage rectifier. If that doesn't work, you'll get only the load of the heaters, and no output. If the plates on it are glowing red, the filter caps are shorted and it needs to be shut off immediately.

You may be able to piece together reasonable voltages based on similar amps. Find something else that uses the same output tubes and you'll probably be in the neighborhood.

 

[bfreemannh]

It is pulling .75 amps. The rectifier plates are not glowing, only two little filaments on the very top of it.
None of the five smaller tubes glow at all.
I assume the taller tubes (188) are the outputs? Does this look like a push pull configuration? This might help me narrow down my selection of similar configurations.
I guess it wouldn't hurt to order a new tube. I will also start testing caps but my tester doesn't have enough voltage to really test them properly. I'll at least get capacitance and ESR reading or know if they are open or shorted. It's a start. If all the smaller tubes are the same (I think they are) I will try swapping them around and see if I can get any signs of output.

 

[Tom Bavis]

I looked up the Stereodyne 40 - it has a different front panel, same tubes (5x 12AX7, 4x 6BQ5, 5AR4), though arranged differently. Like this one, it appears to be from a Japanese manufacturer.

 

[gadget73]

yeah it'll be push pull.

Its possible that the small tubes have DC heaters. Looking at the pic, I see what looks like a big selenium rectifier there in the back corner. Chase out the leads from that and see if it doesn't go through a filter cap and then up to the small tubes. If it does, its a fair chance that its the heater rectifier and its gone TU. Should be easy enough to confirm. Those small tubes look like 12AX7's or 12AU7's. Heater is pin 4, 5 and 9, depending how its wired. For 12v operation, it uses 4 and 5. For 6v operation, 4 and 5 are tied together, and 9 is the other end. Just stab the voltmeter into those pins and see what you get.

I wouldn't even bother with testing those caps. If they're original, they fail the age test. It would be interesting to see what they do on modern test gear though. My capacitor tester was built in the 1930s, and it does everything with brute force and ignorance. Its also got uninsulated alligator clip test leads, and it will put upwards of 600v on them so you tend to tread carefully with that thing.

 

[bfreemannh]

Progress!!!
I swapped the smokey 12AX7 down to the lower slot. I then had right channel audio.
I then swapped smokey with the tube next to it. Same result, right channel audio only and no noticeable change in sound. Total play time less then 2 minutes. made no changes and tuned it back on for further testing, now not working like before. Tried swapping tube again and rocked the others for possible bad connection.

Back to where I started.
I was surprised to see all Nichicon caps in this roach. I need to buy a real cap tester, like an older Sencore or something that can push some voltage. I hate the thought of having to shotgun all the caps and never knowing the original sound.
I just printed the datasheets for the 7189 and 12AX7 tubes, so I guess it's time to start probing around and get intimate with the layout of the circuitry. I will try to hunt down one or two of each, for replacements.

I know this amplifier is nothing special but this will be my first tube restoration and I expect to learn a lot from it. I might add a Bluetooth receiver to it, after I get it running properly, to make it a nice little stand-alone bookshelf amp.

Here is some pics of the chassis. Maybe this will help with some ideas.

 

[FMB42]

It's good to hear you're making headway.

I definitely think it's worth the effort to bring it back into service. Btw, it looks pretty darn clean under the hood too.

 

[bfreemannh]

Thanks. I think I can clean up the upper deck with some naval-jelly, should come out ok.
I just ordered a couple of 12AX7 tubes from thetubestore.com. They seemed to have the best prices and selection. Too bad not in the US.

I need to inventory the axial caps and draw a map. Can someone shed some light on those large caps? They have three leads...is there two values in each cap (cant read until removed).

 

[bfreemannh]

The larger caps are a 40 + 40 UF 450V multitap. Not an easy find. I wonder if I can stuff these old ones.

 

[gadget73]

Japanese tube gear is usually quite respectable. You might be surprised how that thing sounds once its running.


If thats a 5AR4 rectifier, a 50+50 can will sub for it. Jim McShane has them with I think a 500v rating for like 15 bucks. I have one in a Bogen amp that I just rebuilt. I've bought a number of things from Jim over the years, he's a decent guy to deal with and he has reasonable prices on things. http://mcshanedesign.net/

 

[bfreemannh]

The replacement 12ax7 tube made no difference, the amp is still silent. So I just ordered all the capacitors required to recap, from Justradios. They even had the 40+40s caps. Now if I could just find a good tube tester. I am looking for a Sencore TC-28 Mighty Mite, if anyone knows of one for sale.

 

[bfreemannh]

It Lives!!!!
I replaced the smokey tube and all of the original Nichicon electrolytics. It still has all the original plastic low value caps, though. I have replacements for them but not sure if I need them, just yet. Radio museum has this amplifier listed at 45W. It is currently outputting 22.5w on each channel. It's not running at half power, is it? I am also not able to clip a 1000Hz sign-wave at full volume, is this by design? My plan is to electrically clean all connections and pots, next. Also, the loudness switch and stereo/mono switch seem to have no effect, need to investigate that, too. I sure could use some direction on how to check the bias at some point, if anyone would be willing to help.

 

[bfreemannh]

OK, all the tube sockets, pins, RCA jacks and pots have been cleaned. I will say that none of the pots exhibit any signs of cracking or sudden changes. I feel pretty confident they are in good working order. The only real change is that the loudness switch seems to work a little bit. My chief complaint at the moment, is that the balance doesn't seem do much. Turning the balance seems to alter tone a little without changing the amplitude on either channel. This peculiar result can be watched on my scope. Both channels remain at the same volume, but I can see the shape of the signal alter equally on both channels. I suspect the next logical step is to start testing and replacing the small value plastic caps coupled to the back of the balance pot. I also need to test the Stereo/Mono settings more closely, as I am not hearing any difference.

 

[SixCats!]

Hi all,

I was inspired by this old thread as it reminded me that I have a very nice original conditon Realistic SAF-40B Tube Receiver that (if memory serves) I did have checked out/serviced by a qualified Tech many years ago. However, I also later recall putting this Amp aside (in storage years ago) as the unit was acting up and MAY have had some sort of a Channel issue (sound popping in and out). So today (Tuesday 1/22/2019) being a very frigid cold day here in Maine, I decided to dig out the SAF-40B. I pulled all the Tubes and De-oxit all the Sockets, Switches, Buttons, connections, etc. I hooked her up to my Polk 10 Monitors and powered her up. Ahhhhh, nice! Everything was working fine. Shortly thereafter, one of the channels again stopped working! Arrrrrrh!
I checked all the connections and everything appeared correct. I decided to shut down the unit (having just flipped off the power switch) when the Channel popped back on! I immediately flicked the power switch back on and the (Left) Channel continued to work/play as normal. I "worked" all the switches/knobs/buttons and experienced no future issues/problems. Ummmmm. At any rate, I am just going to let the Amp play for the day and see if any issues arise. Thus far, the ol' SAF-40B is sounding/playing very good. I always expect it's the BALANCE Control that seems to cause these type of issues. I've worked the Balance Control back and forth and I've experienced no problems. I hope the ol' Amp continues to work without any further issues. Nice lil' Amp!



Oooh, almost forgot, I THINK I have the Speaker wires connected correctly to the back of the Amp. I find it a bit confusing as it's not marked. Also, might anyone be able to explain the PHASE button on back of Amp (it use) ? Thanks.

(Borrowed Picture, thank you Radio Museum)


I have POSITIVE wire connected (per this photo) to the #1 screw
and the NEG. wire connected to screw #2

I assume the RED wire (shown in the MIDDLE of terminal) is the 8 Ohm setting ?

My Amp is set up the same way.

SixCats!