Jess Oliver's legacy - AMPEG PORTAFLEX CLUB part 9

[JimmyM]

#328 sgiacomo

The online B-15R manual has that brochure about tubes included. Ignore the part about changing them regularly, though. Change them when they break or get crappy sounding, and not a minute sooner.

[beans-on-toast]

Originally Posted by coreyfyfe

Still haven't figured out my fuse blowing problem. It's a short or an exposed wire somewhere, but I haven't nailed it down yet. I took some video of powering it up to try to capture the point of flash, but I haven't had much time to work on it. Anyways, I think I may have found something tonight (click for larger version). The red boxes show the flash I was able to capture, is it just me or does it look to be centered around the heater wires for the rectifier? Or could it be beneath the board? I'm a bit at a loss here and hoping I don't have to tear it all apart to figure this out.

I wish I could say that I see something Corey. Wherever it is shorting, you should see some scorch marks. If there is nothing evident on top, maybe it is on the bottom. Sometimes a dental mirror and a bright light can be used to inspect the bottom. Getting you hands on a fiber optic scope would be the best way to look under there.

The RED twisted pair going to pin-4 and pin-6 of the rectifier are the high voltage secondary wires. The YELLOW wires are the 5VAC rectifier heater wires going to pin-2 and pin-8 of the rectifier. The GREEN pair is the 6.3VAC heater wires for the pre-amp and power tubes.

There is a kink in the green wire near where it emerges through the hole. You could have an arc from one wire to the chassis, another wire, or something else. Or if you have a broken wire it could be arcing at the break. Is that just a bend in the wire? Feel it and see if the wire is broken there. Check the other wires as well. Wiggle them a bit along the length and see if they feel solid along the length.

I would carefully try to reposition the wires so that, they are not in contact with each other. For instance, the yellow and the green wire are touching. If you can, give them a little separation. Lift the red twisted pair off the board and away from anything else. It would help even if you can move things out of the way temporarily for the purpose of testing.

In your second pic, that solder joint where the yellow wire is going into the board looks a bit dull. I can't tell from the pic if it is just dirt or if the joint is bad. I would clean all those joints along the bottom with a Q-Tip and some acetone, alcohol, or even some vodka so that you can inspect them carefully. An errant strand of wire or a blob of solder in the wrong place underneath could be causing a short. In the case of that yellow wire at the bottom, try unsoldering it, cleaning the board, and re-soldering it, ensuring that the wire is not sticking too far through the board. Same for the red and white wires next to it.

Try using a solid state module instead of the rectifier tube. If it is arcing at the tube socket, this might help as it opens the heater circuit.

If you can remove the power transformer bolts, you can lift the transformer off the chassis a crack and check out the condition of the plastic sheathing on the wires where they emerge from the transformer. You won't be able to see much but it might be worth a try.

If all else fails, you just might have to remove the board. Not an easy thing to do.

[beans-on-toast]

Originally Posted by sgiacomo

Greetings! Checked on another serial number date thread but no luck so figured I would post here too. I ran across a mint B15R with an X in the serial number fourth digit. I emailed LOUD tech support and got this response: When SLM (Saint Louis Music) implemented their serialization in 1988, the fourth letter was the country, and was either U, D, W, or Y. While we have seen a few amps that had a X as the country designation, unfortunately, we don’t have any documentation on what it signified. However, the serial number does populate the B-15 parts list.

Very nice find, a new old stock amp. Sometimes the serial numbers do get mucked up. If the store has the original box, the serial number should be on that as well. You can compare them. You can always send a personal message to Jerrold Tiers and ask him if he has any insight. He worked at SLM when that amp was being produced.

[sgiacomo]

I sent Jerrold a PM and he replied but didn't know about the serial number. Thanks for the info on the tubes, I found the material online just thought it was kinda neat to have original printed material from 15 years ago. Don't have the box though.

[coreyfyfe]

Originally Posted by beans-on-toast

I wish I could say that I see something Corey. Wherever it is shorting, you should see some scorch marks. If there is nothing evident on top, maybe it is on the bottom. Sometimes a dental mirror and a bright light can be used to inspect the bottom. Getting you hands on a fiber optic scope would be the best way to look under there.

I wish I could say I see something too The idea to take a video and try to pinpoint it was a bit hopeful on my part, but worth a shot I guess. I'll try the dental mirror trick.

Originally Posted by beans-on-toast

There is a kink in the green wire near where it emerges through the hole. You could have an arc from one wire to the chassis, another wire, or something else. Or if you have a broken wire it could be arcing at the break. Is that just a bend in the wire? Feel it and see if the wire is broken there. Check the other wires as well. Wiggle them a bit along the length and see if they feel solid along the length.

They feel pretty solid, as far as I can tell. When I re-sheathed the green heater wires I had them pulled straight and checked along the length of them the best I could for breaks and they seemed okay. I didn't feel any breaks in the yellow wires, but I'll give it all another going over when I have some time tonight.

Originally Posted by beans-on-toast

I would carefully try to reposition the wires so that, they are not in contact with each other. For instance, the yellow and the green wire are touching. If you can, give them a little separation. Lift the red twisted pair off the board and away from anything else. It would help even if you can move things out of the way temporarily for the purpose of testing.

That might be my best bet I suppose. Move things around and fire it up again, see if I can get a better idea of what is going on.

Originally Posted by beans-on-toast

In your second pic, that solder joint where the yellow wire is going into the board looks a bit dull. I can't tell from the pic if it is just dirt or if the joint is bad. I would clean all those joints along the bottom with a Q-Tip and some acetone, alcohol, or even some vodka so that you can inspect them carefully. An errant strand of wire or a blob of solder in the wrong place underneath could be causing a short. In the case of that yellow wire at the bottom, try unsoldering it, cleaning the board, and re-soldering it, ensuring that the wire is not sticking too far through the board. Same for the red and white wires next to it.

The solder does look a little blobby around that connection, but until I can get a view of the underside I can't comment there. I tried to clean up the board in general with some circuit wash, but this amp has certainly been through some trouble in the past. It looks like at some point a cap blew as there is a big singed spot on the board under one of the power supply electrolytic caps and another spot further down that's darkened as has a small chunk missing.

Originally Posted by beans-on-toast

Try using a solid state module instead of the rectifier tube. If it is arcing at the tube socket, this might help as it opens the heater circuit.

There's no tube in there now, so the circuit should be open, but I can plug the SS module in and make sure.

Originally Posted by beans-on-toast

If you can remove the power transformer bolts, you can lift the transformer off the chassis a crack and check out the condition of the plastic sheathing on the wires where they emerge from the transformer. You won't be able to see much but it might be worth a try.

If all else fails, you just might have to remove the board. Not an easy thing to do.

I lifted the transformer this morning and stuff looks okay underneath. A little darkening on one of the yellow wires, but I can't tell if that's just dirt or from how it bends around the opening for the transformer wires. I'm really hoping I won't have to lift the board.

[beans-on-toast]

Originally Posted by coreyfyfe

I lifted the transformer this morning and stuff looks okay underneath. A little darkening on one of the yellow wires, but I can't tell if that's just dirt or from how it bends around the opening for the transformer wires. I'm really hoping I won't have to lift the board.

The video was a good idea but it seems like you need a faster frame rate to capture it since the event is so brief.

Any bend close to the transformer or where a wire passes through the circuit board would be places to focus your attention. One test you could do is pull the transformer off again and look with the lights dimmed when you power it up. If you see no sparking there, you can rule out that area.

[ddbassGA]

Heads up for a B-15R near Athens, GA. Asking price $850. Not mine and no affiliation. I do plan to see it tomorrow or Thurs, but unlikely that I will make a play for it myself, since I'm broke. I'll post what I see here and PM me if you're interested.

[Farfetched]

Had a chance to take a closer look at my 2 new B-15Ns and came up with a couple of qs
-Are the tube sockets supposed to be different than pre 65s? They are definitely quite different than my 65.
-Sylvanias labeled made in West Germany and International Service Master tubes. Are these relabeled Brimars?
-I know they're brittle, but any tips on taking the metal Ampeg logo off the cab?

[beans-on-toast]

Originally Posted by Farfetched

Are the tube sockets supposed to be different than pre 65s? They are definitely quite different than my 65.

How are they different? It would help to answer your question if you could post I pic. If they have the same type of revet holding the tube socket in place, they are likely originals. For the most part, the same sockets were used on a lot of Ampeg products.

Sylvanias labeled made in West Germany and International Service Master tubes. Are these relabeled Brimars?

You might find something by checking out this tube library and compare the tubes and what is inside them with what you have. ISM bought tubes and relabeled them. In the 1980's there were a lot of Russian tubes being relabeled.

I know they're brittle, but any tips on taking the metal Ampeg logo off the cab?

Yes they are very brittle. Made of pot metal. I insert a hardware store razor blade close to where the pins are and gently pry. You have to alternate from one pin to the next, gently lifting the logo away from the cab a small amount at a time. Patience is really important. I can't stress how important it is to move it just a fraction of a mm at a time. If you pull it away too much the stress will crack the metal. The three pins are nails imbedded in the metal. They can break out as well.

When the logo is far enough from the cab, I use as wide a putty knife as I can to help force it out.

I'll post some images below.

[beans-on-toast]

This will give you an idea where the pins are located on the vintage metal script logo. There are different approaches to take when repairing a logo. They can be soldered but I haven't had much luck doing that. This is what I've done.

Start with a good cleaning. I use acetone. I buy some fine brass mesh from a train hobby shop. You can cut the brass with scissors to any size that you need.






I apply a small amount of epoxy on the top and bottom. The holes in the brass help lock the epoxy in place. I use an automotive product called JB Weld, a two part epoxy. For some reason this product sticks to pot metal while other products that I tried don't. In addition to the break, I reinforce the pins and build up one or two hollow spots. This helps the logo lie flat with no weak bridges that will break if pressure is put on the logo from the front. The key is to not let this sandwich get too thick. You can shave them down. You want the logo to look like it is flat against the tolex.

Another approach, which I don't have any pics of, is to cut a backing plate in the shape of the logo, only slightly smaller and glue the logo to it.





This shows where the pins are located on the logo.






Here is a repaired logo. You have to look carefully to see the crack. These things are usually in such rough shape that a hairline crack is not a big deal.

[Farfetched]

I don't have them in front of me, but the biggest difference is that that it looks like the tube sockets on my 65 was 'under' mounted. Whereas the other later ones that I have seemed more robust and 'over' mounted so you can see the little brackets, where the rivets go, go over the chassis.

[beans-on-toast]

That's normal for the 67. The socket was top mounted via a silver metal ring assembly. The socket is raised above the chassis. With the early 65 it was mounted from below and flush with the chassis.

[Vintage-Blue]

Originally Posted by Farfetched

I don't have them in front of me, but the biggest difference is that that it looks like the tube sockets on my 65 was 'under' mounted. Whereas the other later ones that I have seemed more robust and 'over' mounted so you can see the little brackets, where the rivets go, go over the chassis.

I'm not sure why they made the change but it looks like they made that switch right around 1965, which also is roughly when they switched from eyelet board to printed circuit boards on the B15s. My two '64 B15NCs (eyelet board) both have the under-mounted tube sockets whereas my B15NFs (PCB) have top mounted sockets. I wonder if it was somehow cheaper/easier to do it from the top?

[beans-on-toast]

Top mounting makes repairing the amp easier. It allows you to change one socket without removing the PC board. If it mounted from inside the chassis, you would have to unsolder all the sockets and remove the board to get at the socket.

[Farfetched]

How are the logos mounted in the Transitional ones (where the logo is in the grill cloth)? Is it just kind of nailed in the baffle?

[coreyfyfe]

Originally Posted by Vintage-Blue

I'm not sure why they made the change but it looks like they made that switch right around 1965, which also is roughly when they switched from eyelet board to printed circuit boards on the B15s. My two '64 B15NCs (eyelet board) both have the under-mounted tube sockets whereas my B15NFs (PCB) have top mounted sockets. I wonder if it was somehow cheaper/easier to do it from the top?

My 65 NC has a PCB and top mounted sockets. The pot date codes span the last couple week of 64 and the first week of 65, so it must have been right around early 65 that they made the change.

[beans-on-toast]

The logo is mounted the same way. The ones that came later had the rectangular logo like you also see on the SVT cabs. It had four screws which made life a lot easier.

Check the inside of the baffle to see if the pins went through. If they did, you might try tapping with a nail set from the back.

One other thing, sometimes the pins are mounted on an angle. They aren't always mounted at right angles to the back surface of the logo. You can see this in one of the images above. This complicated matters. Whether pulling or pushing, apply force along the line of the pin as much as you can.

[beans-on-toast]

I would think that the PCB and top mounted sockets went together on the B-15. You never know about transitional amps. This type of top mounted socket on Ampeg amps dates to the 50's. The SVT's and other amps had them.

It is interesting that they went with the bottom mount for the early B-15's. Maybe the cleaner look was part of the design concept. It helps un-clutter the chrome.

[kuratacus]

just a comment on the logo's is there any place that sell EXACT reproductions of the logo? i got a logo from fliptops to replace one on an old rocket and though it's really close it's not the same as the logo used in the 60's. more skewed and rounded. I'd like to get one or even a broken original and make a mold cast so i can make resin casts that can be painted to look like old tarnished metal.

i have an A PEG from the rocket anyone have an M ahahahah i dare not try and remove the logo from my B15

[christw]

Originally Posted by kuratacus

just a comment on the logo's is there any place that sell EXACT reproductions of the logo? i got a logo from fliptops to replace one on an old rocket and though it's really close it's not the same as the logo used in the 60's. more skewed and rounded. I'd like to get one or even a broken original and make a mold cast so i can make resin casts that can be painted to look like old tarnished metal.

i have an A PEG from the rocket anyone have an M ahahahah i dare not try and remove the logo from my B15

I have a replacement on my B-12XTC cab from Fliptops but it's definitely not exact. I had to make a new hole for one of the studs on the back of the logo to fit it and broke it in two anyways.

If anyone really needs a vintage to clone, I can pull the one off of my B-15 and make a mold while I'm working on the flappy bit of tolex in the port.