DS160 Sound

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

Darrell,
Seeburg fused the earlier version of that amp at 2 A MDL--
IMHO, the failure of both tubes is a coincidence---I do not think one, "took out" the other --
Is it safe--I dono, as there could be something else wrong--
Ron Rich

Ron

Thank you. Looking for in line fuse holders and fuses, Shack is all out of both items. Not many other choices in this town. Called two auto parts stores and ACE Harware and no go there either. May have to get them on line!

Best
Darrell

Ron, Darrel it is possible for a high current tube to kill a rectifier in an this sort of design. In the absence of a fuse the rect tube's internal resistance becomes the "fuse of last resort".

I've seen this repeatedly in old house PA systems used in the theaters and schools that I repaired back in the late 70-80's where all that mattered was 'getting it going" and a larger fuse (or tin foil) was used.

The question here is whether the tube's short was in an element that could facilitate high current flow -G1-G2 short, or some lower level leakage of G1 to cathode which probably would not. Many tube testers cannot reveal the difference.

As for it being "safe" to install new tubes and try again, personally I would prefer to have a fuse in the circuit first, but if you connect a meter to C120D -the first filter coming out of the rect tube and power up watching for proper voltage and any fireworks in the 5U4 you can go for it.

Rob

Rob,
You are correct--I was thinking of a fused unit---
Darrell,
Rat Shack does not have any because I purchased the last package yesterday---you can use a fuse block (clip).
RS # 270-0742--that's the number for a 4 pack, I know that they also come in either two packs, or one packs--in the compartment right next to the 4 pack-- call them with the part #, and you have "a chance" they will find it-- Ron Rich

Rob & Ron

Picked up some in line fuse holders at Farm & Fleet and now need to find the fuses! I will not do anything until the amp is fused and then I will connect a meter to C120D -the first filter coming out of the rect tube and power up watching for proper voltage and any fireworks in the 5U4!

Bummer, just called Shack and they do not even carry that part in this town! Just checked on line and this is message I get "We're sorry. Your search for “270-0742” found 0 items." When Ron said he bought the last package, I did not think he meant the "last package" the entire chain had!

Thank you very much for the help. Will let you know what happens in this ongoing saga.

Mark, our wives and myself are going to the Chicagoland Show in St Charles this Saturday 11/10/2012. Should be a great time!

Best
Darrell

Rob

Put 2.0A Slo Blo fuse in line.

What reading should we be getting from C120D? We are not getting any readings from any of the filter capicitors?

Is this the end of the line for the transformer or is there further testing to be done?

Thank you
Darrell

Darrell, If you look at this schematic: http://www.verntisdale.com/schem/shfa5.jpg You should see something north of 370 vdc, probably around 410vdc. Anything anywhere near that should be a good sign.

So, if the 5U4 is lit and not acting up there should be high voltage at Pin 8 which leads to the first filter. If you look at the schematic, the circuit here is pretty simple.

Earlier someone named Mark said that he measured 700vac at pins 4&6 on the 5U4. This, along with a lighted 5U4 indicates the transformer is good so you need to check for missing pin connectors in the tube socket, broken connections etc.

Be careful in this section as the voltages are lethal. Use only one hand and keep the other away from the chassis or any source of ground.

Let us know how it goes.

Rob

Rob

We placed the inline fuse at the square P101 (Power Imput), Is this the correct location and is 2.0 SLO BLO OK? Shack is supposed to get the 1.5s in tomorrow.

You are correct, the 5U4 is lit up and acting normal.

Will check for missing pin connectors in the tube socket, broken connections etc.

Glad to hear transformer should be OK

Will let you know what we find. Thanks for the schematic. Are there any fuses I should add to protect our Seeburg KS200>

Best
Darrell

Darrell, that new fuse should be on the primary (AC line) of the power tran on the amp.

As for fusing, here is what I use in the selection receivers:

Low-Dc from rectifier 500ma slo in each leg from the tran to the rectifier. This assumes that you have replaced the original bridge with a silicon diode package. If you haven't replaced it, a single 500ma on the rect's output should be OK.


150 VAC. This powers the plate circuits of both the trip and steppers. I use 1 amp/fast. My situation is a little different from original in that there are no 2050 tubes and the circuit uses SCR's which do pass higher current.

25 VAC. This feeds: latch solenoid, several credit coils, the scan and the drum. The credit lights are derived from this source. I use 4amp/slo.

5 VAC. On your machine this only feeds the three "taillights" and category lights. I use 3 amp/slo

6.3 VAC. This is for the amp filaments. I use 4 amp/slo.

Rob/NYC

PS: If you are just using that machine w/out wallboxes, you can use a lower main fuse. Go from 5 amp to 3 amp/slo and I add a 1-1/2 amp/slo to the florescent ballast input.

Rob

The new fuse is on the primary (AC line) of the power transformer on the amp side of P101.

Is it possible that the "dull roar & pop" I heard was the sound of both audio amps going bad?

Thank you for the break down on fuses for the selector receivers.

Its hard to believe that Seeburg was to cheap to properly fuse their product! But, Ron verifies that is the case.

Best
Darrell

Ron Rob Mark

While Mark was at my house the other night we decided to listen to the good DS160 while we worked on the problem DS160 AMP. After several records, OH NO, the dreaded "dull roar & pop" and now we had two bad amps with no sound! Mark checked the 5u4 tubes and found one was shorting out. He took the 6973 tubes home and found that 3 of the 8 were shorted out! I put the inline fuse in the second DS160, put the good 5u4 and 4 good 6973 tubes in and guardedly turned the phono on.

Sounds great. One down & one to go.

Thanks to all for their excellent help and advice.

Best
Darrell

Ron

Went to shack and of course no 1.5A SLO BLO fuses came in and they are still out of 2.0A SLO BLO fuses!

Rob suggested 1.5A and you said Seeburg used 2.0A in some other AMP. Is my thinking correct that the 1.5A fuse is approximately 25 % safer than the 2.0A fuse?

Best
Darrell

Darrell,
Yea--"safer"--IF it will hold--might try it in the working (well) amp, and see if it holds for several hours of play-time--
Ron Rich

Ron

I have 2A Slo Blo in the amps protecting them and if I ever get my hands on some 1.5A Slo Blo I may try them out.

On a sad note, , I put a good 5u4 and 4 good 6973 tubes in and guardedly turned the orininal bad amp phono on. Alas, I still have no sound? All tubes light up. Would the next step be to check the audio transformers?

Had a nice time at St Charles show, picked up a few records and some 455 bulbs for taillights and a reproduction glass for "our" (my wife's) KS200.

Best
Darrell