DS160 Sound

Cranked up my Seeburg DS160 and on the first selection when the mech traveled to the record there was a "dull roar" sound. WHen the record began to play there was no sound other than a very very faint sound you could only hear if it was totally silent in the house. Pulled mute plug with record playing and no sound. Checked 5U4 tube and determined it was not lit. Pulled this tube and went to other DS160 and exchanged 5U4 tubes, neither tube not lit up. and I had no sound in both phonos. I then again exchanged the 5U4 tubes. I now still had no sound in the first DS160, but the second one had sound and the 5U4 tube lit up.

I suspect I may have two problems here, 1) Bad 5U4 tube and 2) shorted or open high voltage supply/shorted or open low voltage supply.

Solution to 1) replace with new tube after fixing item 2).

How would I check these two voltages? (I know I need to use a multimeter )

Thanks
Darrell

Let's try to sort out what is going on here.

First, if the 5U4 is not lit you have NO sound from the amp. What you hear is needle chatter directly from the stylus.

If you placed the 5U4 from the "dead" amp into another and it worked the tube becomes prime suspect.

If the 5U4 from the 'good" amp does not light in the dead amp check the fuse. If that is blown you may have a shorted filter cap -not uncommon in these old tube amps.

At this point unplug the machine and use your multimeter to test from the filter caps to ground looking for shorts.

Before testing for resistance, first set the meter to DC voltage and test all those filter terminal for the presence of any lingering voltage. This is important to prevent damage to the meter and false readings because the meter puts out a small voltage to test resistance and extraneous voltage from the circuit will confuse things.

if you find a shorted filter, the solution is obvious.

If not, then check for the minus 30vdc from the small rectifier. Again make sure a good fuse is in the amp. Then remove the 5U4 and get the phono playing. the 30 volts should appear at C122. BTW: That old diode should be replaced with a modern silicon one. The reason this voltage is important is that without it the output tubes have no bias and will greatly over-conduct and overload the power supply.

That 'dull roar" may indicate a shorted output transformer. If you are reading short @ C120c try disconnecting each output tran and read for shorts.

Its also possible that an output tube has shorted, this would blow the amp fuse.

There are other, more involved tests, but these should at least point out the section. This is a straightforward problem, but it may be a bit costly if a transformer is the cause.

Rob/NYC

Rob

Thank you for info. Several projects going on. Will let you know what my findings are.

Amp has been recapped. If you are referring to Diode "CR101" it has been replaced when it was capped.

Getting a little confused, cannot locate 5 amp pigail fuse for mech that is identified on page 2468E of the manual?

The stepper 3.2 has a 3.0 fuse in it and it checks OK. The Tormat 5.0 amp also checks OK.

I do not think there is any need to check the 1/2 amp Slo Blo or 1-6/10amp fuses in the UPU.

Best
Darrell

Darrell,
You think you are "confused"--wow, you sure have me confused--
First--where did you hear the "dull roar" from --speakers ??
The five amp pigtail fuse MUST be on the mechanism --lower right hand side, connected to the switch plate and the lower"foot" of the terminal strip, and the lowest terminal on the strip--BTW--it has nothing to do with "audio" ?? Nor does the 3, or 3.2 amp stepper fuse ? What is the "Tormat 5 amp" fuse-??-are you speaking here of the Tormat Selector Unit (TSU), main fuse ? If so, and it were bad, you would have "nothing"--no lights, motor, or anything else--including audio.
If neither tube lights up in the "bad amp" but both do in the good amp, I would check the connection that supplies voltage from the TSU to the amp--these sometimes tend to "fail"--
There (unfortunately) is no fuse in the correct amplifier, for the DS, of any kind !
Ron Rich

Darrell,
You think you are "confused"--wow, you sure have me confused--
First--where did you hear the "dull roar" from --speakers ??
The five amp pigtail fuse MUST be on the mechanism --lower right hand side, connected to the switch plate and the lower"foot" of the terminal strip, and the lowest terminal on the strip--BTW--it has nothing to do with "audio" ?? Nor does the 3, or 3.2 amp stepper fuse ? What is the "Tormat 5 amp" fuse-??-are you speaking here of the Tormat Selector Unit (TSU), main fuse ? If so, and it were bad, you would have "nothing"--no lights, motor, or anything else--including audio.
If neither tube lights up in the "bad amp" but both do in the good amp, I would check the connection that supplies voltage from the TSU to the amp--these sometimes tend to "fail"--
There (unfortunately) is no fuse in the correct amplifier, for the DS, of any kind !
Ron Rich

Morning Ron

Rob said: "If the 5U4 from the 'good" amp does not light in the dead amp check the fuse." I am trying to get to the fuse Rob refers to and I do not see any in the amp to check?

The 5A is in the TSU and the 3.0 is for the stepper.

When the mech started to scan the "dull roar" appeared to come from the area of the mech(?) and just as the mech selcted the record there was a poppinng sound and all audio went away (other than very very faint music that Rob refered to as needle chatter)?

The tube from the problem amp will not work in either phono. The tube from the good amp does not light up in the bad amp but, does light up and work fine in the good amp.

Best
Darrell

Darrell,
As I wrote above--there is NO fuse in the amplifier, on that model phono---
and like I said--check for 5U4 filament voltage ( with the 5U4 removed, but the mechanism motor running) through the square plug, between the amp and TSU.
P.S. Toss the known bad tube out--as plugging it in to a "good" amp, could cause problems to a good amp !
Ron Rich

Ron

Are you referring to the 63 VDC between pins 4 & 6 of 5U4 tube and 4 studs on the square plug that connects the Amp to the TSU?

Thanks
Darrell

Well,yea--I think maybe--but, there should be no 63vdc at that plug???--one "side" should be "117 ac", and the other 5.3 AC, when the motor is running, only--Ron Rich

Ron

Schematic shows 5 VAC going to 2 & 8 pins. I do not see the 117 VAC but, guess you mean pins 4 & 6 for the 117 VAC.

Pins 2 & 8 have the 5AC. Pins 4 & 6 have between 11 & 15AC except when the mech reverses while scanning, at which time the voltage jumps as high as 199AC.

Re-checked 5.3 voltage at 2 & 8 and 117 at square between TSU & Amp. 5U4 tube is now lit and has 700 AC across pins 4 & 6. Still no sound. How do we check low or high voltage supply if that is next step? or where do we go from here?

Darrell

Hi all: i am working on this with Darrell. the 5u4 gets heater lit now. the one we took out was definitly bad. open heater. the input to the t101 is line voltage as Darrell mentioned we get 700v ac across pins 4 and 6. i am not sure where we are to follow the power supply circuit out from here. We visually checked all the components arround the rectifier cr101, and it nor the cpacitors looked bad (c122,121). looking at the schematic, it would be nice to know what voltages i should expect under playing load. The manual suggests that it is a problem with the low or high voltage output. i take that the side of the circuit that has the heater voltage coming off is the low voltage. and the other side of the transformer is the high. but i can only see -30 and -35v on it. I dont know what z and y voltage is. Thanks Mark

Hi all: we have tested the 6973 tubes and have 2 that are showing shorts. I need to know what other components would go out. I am not sure if 6973 took out the 5u4 or visa-versa. Did this failure take out something else? and if we replace the bad 6973, will the new ones just fail right away. please HELP. i am going nuts! Mark

Relax, the 6973's can kill the rectifier -but not the other way around.

This is a case where Seeburg's "economical" application of fusing leads to a longterm failure potential.

FWIW: You should add a fuse to the AC mains input on that amp, 1-1/2 amp-slo would be fine. Just use an inline holder.

Rob/NYC

Rob, and all,
A word or two about Seeburg's ( and I would imagine, other companies) fusing practices.
They would submit new designs to UL for "approval" with minimum fusing. In most cases, UL would require additional fusing, but somehow the "tube type Tormat system" (which contained these un-fused amps) got through with no others required. Seeburg's main concern, was cost--both for the fuse, and any obligation that they may incur in warranty costs ( the 5 amp "pigtail" added to the ground circuit was to protect the Tormat against burn-up during the warranty period).
Their thinking on fuses usually was to use the maximum size fuse possible, as they did not want fuses "blowing for no reason".
I had more than one "dis-agreement" with the "Production Foreman", over very small cost items that were, IMHO, necessary to assure quality. In one instance, we argued for days over what he admitted "cost less than 1/8 th cent per jukebox". Since he was way above me in "pecking order", I enlisted a couple of QA engineers help, and won that one --but I lost several others.
He was a great guy, but he was strictly a "bean counter". I used to call him "Mr. C."--for Mr. "Counter"--but since his last name began with a C, there was never any problems--he never knew--
Ron Rich

Ron & All

I assume there is agreement from all that the AC mains input on the amp should have a 1-1/2 amp-slo blo in line fuse installed.

Is it safe then to install new 6973 tubes and a new 5U4 rectifer tube or is there anything else to check for first?

Is there some common cause (other than age) that would cause a 6973 tube to fail and take out the 5U4?

Best
Darrell