Bad Voltage Regulator on a Rockola 1000

I am close to getting my Rockola 1000 working but I think I have a bad voltage regulator, LM317K, as I am not getting power to the magazine or gripper motor. All my fuses are good and I know both motors work. I am about to order the LM317K regulator but had an install question. Do I just remove the old solder on the 2 pins on the regulator and re-solder to the new pins on the new regulator? It looks like people in the past apply a thermal paste before screwing back onto the heat shield. What thermal paste should I be using for the Rockola 1000 heat sink/voltage regulator?

I don't recall seeing a "two pin" regulator--did you meter the output ?? I would do that first!
Typically, if a "package" is screwed down to a heat sink, and a grease is used, it is a "heat sink grease"--I prefer to use Dow-Corning #5 for this purpose, as it "never" dries --The proper procedure is to remove the old item, open the mounting holes, fit the new item to the holes and heat sink, tighten the mounting screw, then solder legs to the board. Ron Rich

I just replaced the LM317k on my Rock-Ola 1000. I was surprised to see that it was socketed. No soldering was required. But there is a mica insulator that must stay between the heat sink and the body of the regulator. Make a sandwich... The regulator, some thermal paste, the mica sheet, some more thermal paste , then the heat sink. Screw it all together.

Personally, I think this power supply is a bad design. I think Rockola engineers are exceeding the max input voltage on that regulator, so I put a handful of forward biased diodes in series before the LM317 to drop the input voltage a few volts. It doesn't affect the operation but might protect the regulator. I can give you more details if you want.

While I was at it, I put an LED on the output of the LM317 so I have an immediate way to see if the swithed 28v is working. With all the other LEDs on the power supply, it's odd that they ignored the switched 28v. You will find that the LM317 output is off when the 1000 is idle, and on when scanning and playing a record.

Finally, check the connector in the power supply that goes from the LM317 to the PC board with the fuses on it. I found many cold solder joints on that connector... Almost all of them were bad!

Mark.

Before you replace the LM317, check the connector on the PC board in the power supply FIRST.

I mentioned it in passing in my previous post, but check that big white connector for bad solder joints. I had many bad joints on my 1000. I also had a bad LM317, but maybe you'll luck out and resoldering the connector will fix yours and save you the cost of a new LM317.

Another hint. I felt like a dope on this one. When you blow a fuse, check ALL the fuses. When you blow one, you usually blow two. One might look obviously blown while the other looks fine but is actually blown. This is because there is a fuse on each leg of the transformer, so when one blows, the other one will take even more current and blow. I wasted a handful of 1 Amp SloBlo fuses before I realized this. I still have the handprint on my forehead from slapping myself for a dumb mistake.

Mark

OMG,Thanks Mark !!
I now understand why my forehead is concave, rather than convex !! Ron Rich

This is great information, thanks! I am currently waiting for the LM317 to come in the mail but already received the thermal paste. You are correct it is a socket after I looked at it again, that will save time. I will also check the cold joints to the power supply as you stated. I will let you guys know how I make out. Thanks again.

Glad to help.

A word to the wise, apply the thermal paste sparingly. I used a Q-tip and spread it thinly and evenly. When you screw this all together excess paste will squirt out around the edges.

The heat sink is overkill. That LM317 barely gets warm when it is on.

Someone replaced the LM317 on my 1000 once before and was way too generous with the paste. It was all over the place and a mess to clean up.

Another "word to the wise"---??
I hate that white "paste" used by some--much prefer the Dow-corning #5 heat sink grease, which is clear, stays "wet", "forever", and can be applied / removed with a paper towel, or your finger ( new tube I just purchased is marked "NOT for medicinal use"--however, I have used it rather successfully to treat burns--slather it on ASAP, and you won't even know you burned yourself in a few minutes--no scar either--but I am NOT giving anyone "medical advise" here, or anywhere else ! ). Ron Rich

Am I the only one that thought, "I wonder if this regulator is working?" And touched it with my finger, only to hear a sizzling sound. Sounds like your thermal gel would come in handy for that.

Yep--worst case I ever saw, was at the shop I was working at--we had about a 100,000,000 watt soldering iron that was not heated most of the time--only when we intended to use it to bond 12-14 gauge metal to metal--well, unknown who plugged it in, but one of the guys did not realize it was hot, and grabbed it by the shank, near the tip--
I don't know which was loudest--the "sizzle", or his scream ! I don't know why-how I thought to do it, but I grabbed a tube of the heat sink grease, and smothered his very burnt palm in it--an hour later, he said there was no pain, and there was very little visual evidence of a burn -- Ron Rich

I replaced the LM317 with three different regulators and it was a no go. I think I have narrowed my next problem to the play relay on the regulator board (Rectifier PC Board 54875-A). When I slide the scan switch from scan to operate I can hear the play relay clicking, so I am thinking the relay will not close from the play cycle. The play relay from the manual is part C5 electric capacitor 35 WVDC manufacturer part number 4,700 MFD. All the fuses check out good. My question is where can a get a new part to replace the old? It looks like I would remove the old one from the board and solder a new one in if I can find it? Unless you guys have any ideas on what else the check? All the solder joints on the white wire looks good. The Dow Corning #5 is nice but expensive!

Looks to me that you have things "mixed up"--
A "relay" would not be marked a as "C" on the schematic/parts list. A "C" indicates a capacitor, which you have ID'ed as 47,000 MFD x 35 volts, which is available any good "electronics store". A relay is USUALLY indicated with a "K" symbol, although some schematics differ here.
I also seriously doubt the 5 volt system is connected in any way ( other then the relay contacts) to this relay, or it's operation ? Is the 5 volt LED staying on now ??
As for the Dow-Corning #5--the tube I acquired (OK--Liberated, from captivity, at Seeburg), fifty years ago, lasted me till the first of this year--not too costly, as far as I am concerned ( I have enough [which I did purchase !] to last me the rest of my life, and enough that whomever gets my two tubes of it will probably have enough to last the rest of his life too !! ) As the saying goes--a little goes a LOOOOOOOOOONG way ! Ron Rich

The LM317 regulator IC has internal current limiting/ thermal shutdown, and in all my years I've never really came across one that went bad, so I would think other components are at fault.
But educated troubleshooting procedures along with the schematics can be done to narrow down the issue(s) so it shouldn't be a big problem.

Ron, you are correct C5 is a capacitor, my bad I am a newbie at this! Capacitor C5 does make a clicking noise as stated but the relay is K1 (P. C. Relay, SPDT 24 VDC). The 5 V LED stays lite so I think I am good there. I assume P.C. stands for play control relay, this is on the same rectifier board as the C5 capacitor. Could the play control relay be bad if so, can I find this at a good electronic store?

The cap (hopefully!!) makes no noise--the click you hear would come from the relay --and would be a "normal" sound it should make, when energized/de-energized. Without seeing it, it would be my guess that you could find a replacement NTE brand relay, or maybe an OEM type? But, why do you want to replace it --test it first--no use changing it with no results ??? Ron Rich