My DS100 restoration thread.

Hi Brad,
Do da hummmmm getz louder/softer with the VC moving, or not ?
Ron Rich

Brad, your post got me to update the link to the "Hum Files"..and that is a good place to start.

viewtopic.php?f=3&t=6428

If 120Hz it is filtering or excessive load.

If 60hz the cause is usually shielding or heater-cathode leakage.

if you remove the 6BJ6 tubes and the (60Hz) hum goes away it indicates H-K leakage which is a common problem. Simply find which tube is causing the problem and replace it. In these cases the hum will be worst when the tube is conducting heavily such as coming out of squelch or a very loud record.

Rob

Ron, Da Hum dsnt change wit da VC controls

Rob, thanks I should have time tonight or tommorw to read that and start trouble shooting..

Brad

Brad,
By any chance---are you using Russian made 7199's ? I did experience a "flock" of them sometime ago, that were all bad--and "hummmmmmed" like crazy--- Also saw a few Russian 6973's that had problems--don't recall what the problems were now--- Ron Rich

So I ended up swapping all my 6973 and 7199 tubes from my 160 to the 100 and the DS100 amp was perfect, so I swapped out tubes until I found the bad one and it was indeed a 7199 and it is stamped USA not Russia. I do have a question about one 6973 that I bought it is made by Westinghouse, that tube compared to the RCA ones that are running burns probably twice as hot so I guess I am not sure if its a difference in manufacture or if there is a problem with it?

Brad

Hi Brad,
Glad you found it--what "brand" was the bad one ? ( "Brand" names on US branded tubes, are often meaningless as the factories "traded" among themselves, and often re-branded tubes).
If the 6973, has the same size envelope, and it burns hotter in more then one location, I would strongly suspect it has a "short", and would replace it--on the other hand, if any tube placed in the same socket tends to burn hot--there is a problem with either the surrounding caps, and/or resistors. Ron Rich

Brad, it is important to avoid excessive current through the output tubes as this will kill the transformer(s).

Check for around minus 30v on the grid 1 pins which I believe are 6 &3. If one tube shows notably lower reading first swap tubes and if the lower reading follows that tube it is probably gassy and must be replaced. If shorted the grid 1 voltage will be near the plate B+ potential and the plate will "show color" a red or orange. Replace these immediately.

Seeburg design was faulty here. They used fixed bias to get more power from a tube. However, if the tube shorts there is nothing but the resistance of the output transformer to limit current. 6973 Is a last generation, efficient tube, but to achieve that efficiency the grids must be closely spaced making it somewhat delicate. Given the kind of rough treatment jukes often get the 6973 was not a good choice, but RCA was pushing them at the time.

Wurlitzer and Rowe/AMI also used them, but they employed cathode bias which gives a margin of safety.

I inherited a box of over a dozen output trans from a closing operator on Tenth Ave here in the city. Most were from Seeburgs and of that 13-14 only 3 were actually good. The other were asymmetric w/shorted turns.

Be sure to replace the bias diode and filter cap (if you have not already).

Rob

Firstly happy fathers day to all on the board.

Ron,
Unfortunately the markings of manufacture are long gone, just the tube type and country are still visible. As far as the 6973 the envelope is the same, from what I can tell the heater on this is about an 1/8th inch probably six times bigger than the RCA tubes that are in the other locations. On the invoice from where I purchased it they have a note that states This is a substitute tube but tested to 6973 specs, it goes on talking about rockola amps and how there needs to be jumpers etc.. The tube is stamped Westinghouse 6973 made in the usa?

Rob,
I will have to get down there maybe today and test the voltages, also for the bias diode if you are talking about CR101 (Attached) I have not replaced that, if that is the one I am not sure what a viable replacement is for it?

Thanks
Brad

Brad,
If it was a substitute, it would NOT be marked with those tube numbers---
You can use a 1N40004 dode--cathode is the "red dot". Ron Rich

Ron,
I have found the data sheet on the 1n40004 so I know it exists but I cannot find a supplier, do you know where I can purchase some?

Brad

Hi Brad,
Is there no Radio Shack/local electronic supply house, left in your area? There are no RS's left here, but we do have a fairly close, (about 20 minutes drive) independent, electronics store--
All the large electronics houses , such as JameCo, Mouser, DidgaKey, stock them--and I have about 100 of them in stock--(1N4007's)--PM me if you want to purchase some--Ron Rich

Ron,
We might have one or two radio shacks but the last time I was in there all the really sold was cell phones and toys, we have no “Store front” electronic stores that I know about we do have a great online vendor that is in Omaha. I did find my diodes in the pinball parts stash so I am good, man I need to clean that area up

Brad,
I just scrolled up thru the photo you posted, and it appears as if the lower cap MAY not be soldered on the right (-) end where it connects to the 1k resistor ?? Ron Rich

Well I am officially going to close the thread, there are a couple things I am still needing to do like replace the main power cord and I want to replace the chord on the control unit because it is really frayed but other than that it is done!! and I am tired I hope to never do this again at least for a year

NOPE--You NEED to do one more thing--Either, put your name, or the "Seeburg sign", in the slide-in above the word
"presents"-- Ron Rich