Seeburg 100r Recap question/s

I got mine hooked back up and it's sort of working. The good news is it's not blowing the fuse and all my tubes glow. The bad news is the output is very low, almost like the needle tracking noise is as loud as the music. I have tried adjusting the master volume in the back and adjusting the bass/treble (they work). My speaker jack J2 might be flaky, it takes some wiggling to get any output. Do both transformers get warm after being on? One of mine feels cool to the touch after 15 min of being on.

I have a number of backup tubes I've swapped around with no change, although I don't have any 6L6s. When the amp arrived it had a "SST 100 Solid State Equivelent" made by International Servicemaster plugged into the 5U4-G tube. I put in the original 5U4-G and that lights up, I'm afraid to try that SS replacement as I can't find any specs on it.

Do both transformers get warm after being on? One of mine feels cool to the touch after 15 min of being on.

On the amp, typically the B+ tran will warmup and the output -only slightly.

the output is very low, almost like the needle tracking noise is as loud as the music

Obvious questions: What is the stylus situation? What sort of cart is there? Is there noise when you lift the pickup off a record?

Rob

The output transformer is the one that's running fairly cool. It's difficult to tell if the warmth is coming from it or if it's absorbing heat from the 6l6's.

I've actually been meaning to ask if anyone knew which cart I have. I think Ron Rich mentioned it was a later stereo cart. Here is a picture if that helps:



There was an solid state Yamaha stereo amp that had been driving the speakers until I yanked it today for the Mra5. The J2 plug had been cut and was fed directly into the yamaha that was running in Mono mode. With the solid state amp it had very good output, actually too loud for the room if turned all the way up.

The MRA5 will output a fair amount of volume (loud talking level) if set to 25W output and the main volume pot turned all the way up, but no where close to the solid state amp. It's scratchy sounding too... When playback ends it is quiet with only very slight hum.

First thing is if you do not have any external speakers connected, you should have the speaker switch set to 25 watts always.
The cartridge is a Pickering 340D.

As for sound, I see that this machine was modified a fair amount from original state, there are alot of things that it could be in my opinion.

Needle condition?
Since a stereo tone arm was installed, as the 100r was originally mono.
Tube issue? Should have matched 6L6's. The 12AX7 could be bad.
Could be a speaker issue.

Guyz,
There could be a lot of things here, or nothing--The Seeburg ( and most other brand jukes) with tube type amps did not have the volume level of newer SS models.Without hearing it, this is sort of "subjective".
Two things--
The cartridge is not a "340D"--it's a 340--the "D" would indicate "Diamond" needles. It MAY have been a 340-03D, or a standard 340 type, that was modified --can't tell from the photo.
I appears that a "Stereo toe arm" was NOT installed.
Matched 6L6 tubes--not necessary IMHO --
Any tube, can be "bad", as well as other things--the "flaky" speaker plug is worry-some, and can cause a loss of volume, as can any of the "switches" on the amp--and the "squelch switch" on the mechanism (this is a problem,VERY often).
Ron Rich

For matched tubes... Many amplifiers not just in jukeboxes are designed to require power tubes that have similar cathode current. Even tubes of the same type, made at the same time will have variations in their cathode current, this is why matching is highly recommended. Not every amp requires matched tubes, but it never hurts. Most online stores will only charge a few $ for matching.

It definitely could use new Styli, but not really explaining the huge difference in output. The MRA5 outputs at a level that would be very low volume on the solid state it just replaced. The styli are yellow Pfanstiehl model 4728-d7. They are diamond tipped but worn. I have tried 2 different 12ax7 preamp tubes, no change but both could be bad.

I guess I could spring for new tubes by Mesa Boogie. I like their amps and these say these are flat response:
12ax7 - http://www.sweetwater.com/store/detail/MB12AX7
6l6 (matched pair) - http://www.sweetwater.com/store/detail/MB6L6GCD
5u4G - http://www.sweetwater.com/store/detail/MB5U4G

Actually I think my Fender Twin guitar amp has 4 6L6s, maybe i will try 2 from that amp first.

Some things to consider here:

1) It looks like that is one of those adapters that allowed the newer (1966-up) cart to be used in older machine arms. Some of those adapters properly connected both coils of the stereo cart in parallel, some used only one channel and other connected them in-series. The last two will result in much more noise and distortion from stylus and record wear begin noticeable.

That cart measures approx 460 ohms/channel. In parallel it will be half. In series it will be double. Measure at the RCA plug.

Those adapter do not add additional weight to account for the cart being lighter than the original so the arm will not balance properly. This causes it to bias toward the center of a record and results in added wear and distortion.

Level: The later cart had much lower output than the original with mono styli. Original cart was around 30mv and the later one is approx 10-12mv. Even with the original cart, the gain structure of the amp did not permit driving it to distortion. That was intentional. As a test, remove the 6SK7 tube while playing a 'quiet" record. If level goes up a lot the squelch contacts in the mechanism may not be making during play. These are the top set on the vertical stack.

The quality and material of the stylus cantilever -does- affect level. NONE of the copy types that I've tested have the same output as the original Pickering made for Seeburg. You might get similar output by using the high-output styli Stanton/Pickering supplied for their 400 series "disco" carts. This will require cutting away most of the plastic to fit the stylus shank into the Seeburg type cart. It still won't equal the original mono cart and styli, but it will sound a lot better than the copy needles.

Tube balancing: These old amps are not critical at all in this regard. Unless you are driving the amp to maximum output with sine waves, you won't notice a different. I have 8 old Seeburgs on location with tube amps. The tube are a mis-mosh. I've tested each one of maximum undistorted output. Even extreme mismatching makes no audible difference.

The voltage gain tubes however are another matter. The 5879, 6SN7 and 12AX7 need to be strong for full output. In my V-VL amps on location, I replaced the 5879 with a homemade 12AX7 preamp to provide enough amplification to properly drive the AGC and thus level the records.

Rob/NYC

That cart measures approx 460 ohms/channel. In parallel it will be half. In series it will be double. Measure at the RCA plug.

I measured 473 ohms at the RCA. I tried to measure it by pulling the RCA while it was playing and that was a big mistake. A crazy loud sequel came out of the speakers like a smoke alarm. Yikes.

As a test, remove the 6SK7 tube while playing a 'quiet" record. If level goes up a lot the squelch contacts in the mechanism may not be making during play.

No change in volume. MS switch seems to be OK on the mech.

It's playback is so noisy but it sounds like the amp has a lot of output potential. There can be an occasional loud pop or for example the loud sequel when I pulled the RCA, that was LOUD. In playback it sounds like 50% audio and 50% the needle tracking. And I would say the stylus is bad, but it was fine on the other amp.

What's my next course of action? Buy a new Cart? Tubes? Thanks for all the help!

I measured 473 ohms at the RCA.

That means that only one channel is connected. Since there is probably no way of opening whatever was built to adapt that cart to the tonearm you are stuck with a bit more distortion and surface noise if you use this cart.

How did it sound connected to the mag input on a receiver or other amp? If is was good or at least decent considering a likely worn stylus, there is more to be done with that old amp.

Here are the options;

1) New styli for the existing cart. With only one ch connected, it is not ideal. But it is simple and cheap. Some additional weight will be probably be needed to balance that cart properly.

2) Get an original redhead mono cart. Plan on spending at least $100 for the cart and another $80 for the new design styli made in Europe. This will balance and the new styli are stereo compatible though the cart is mono.

3) Change the tonearm to a newer type. The best choice here will be the later type as used in SS160 -end, There are a lot of these around from parted mechs. It is necessary to cut off the tail piece on the "new arm and cut down the existing counterweights to balance the new arm. this will give the best sound and cheapest styli.

4) Change the entire arm-cradle assembly. The only "drop-in" replacement would be one using the "T" needles. These are from 222 to PFEA1U. The assembly will probably cost less than the styli which are specially made for that cart. The sound in mono is decent, but the output is lower than the other options.

You can peruse E-bay and the collector magazines and maybe find one of those "conversion cartridges", But frankly, they are all junk, just repurposed ceramic carts for cheap home stereos.

For home use, option 1 is what I recommend.

This question comes up every month or-so. Styli and carts are the big drawback with Seeburgs. At least with the new styli from Europe the collector's market is in a better position than two years ago when nothing was available for either the mono or T stereo carts.

Rob

I think the stereo to mono adapted cart completely explains the low output when driven by the original amp. The solid state amp had a "mono" button that could double the output to both channels. The sound on that amp was satisfactory and didn't have excessive noise, it just needed new styli. I don't think option 1 is going to cut it for me unless this is still an amp problem. It's surface noise is too much, it's like a poorly tuned radio.

As a test, remove the 6SK7 tube

I took all the tubes I had to a local shop where they were able to test them. Everything was good except for the two 6Sk7 tubes I was swapping. What roles does this tube play in the circuit? When it's removed I still have the noise. I wasn't able to test the 5879 because it's riveted into the chassis.

What ?? How can one "rivet" a glass tube ??? The 5879 SHOULD have a metal cover on it, which "twists off", then, once you can see the "glass", the tube needs to be "pulled out"--
Tube testers do not tell you if a tube is good--only can tell you if it's bad--SK and SL-7 are in the AVC circuit ( RTFM).
Ron Rich

Wow, I had no idea that was just the case and it was a twist lock. I'm an idiot.

But in a moment of clarity I thought of how to separate and troubleshoot the amp vs the cartridge/source. I hooked up a stereo mini to RCA cable from my phone to the amp and put the machine in play mode and engaged the service switch. I got big clear sound from the amp!! Although there is still a very audible underlying hiss with the amp's master volume turned up past 25%. This is what I was hearing when using the cartridge, except it doesn't have the gain my phone is able to output so the hiss is more prominent. I've already hit that master volume pot with Deoxit and it attenuates cleanly. Maybe this is just how the amp sounds in play mode with the volume up that high?

I have no way to judge, what you are hearing ? I suggest, as Rob already has--
1. Obtain a "real" 345-03x cartridge.
2. Obtain a Seeburg "redhead" mono cart. and use the new "stereo compatible" needles.
3. Use one of the newer tone arm/cart. setups.
Ron Rich

I was able to take apart the adapter. I'm not familiar with the pinout, but shouldn't I be able to bridge both + leads and both - leads to convert this down to mono?