DRRI Headscratcher Solved

[diagrammatiks]

for 8 pins the best are the 1 piece molded sockets. they are expensive but if you do any sort of heavy swapping they are worth it.

http://www.partsconnexion.com/CONNEX-74338.html

[Firestorm]

Those are neat. I don't suppose you know the manufacturer...

[Cliff Schecht]

Pretty sure they are Chinese too. Teflon sockets are top of the line but as you would expect they cost the part. $15 a socket is friggin $$$.

If you are retensioning sockets then your tube pins must be out of whack. Grab a pair of pliers or one of those 9-pin socket tools that fixes bent pins before you shove them in the socket and they shouldn't work themselves out of whack so easily. I will say that in the past when I have tried to retension 9-pin Chinese sockets I was not successful while stuff made in the USA retensioned fine.


In my builds I use Cinch stuff almost exclusively if I can source it. They last forever and just don't give me any problems ever. I recycle a lot of them from old defunct equipment too. IME any socket made by Cinch is a good piece, including those ones that are just two thin wafers with holes in one side and pins mounted on the other. Amphenol also makes (made) great stuff but I don't see their sockets as often.

[Structo]

Speaking of sockets.

For you guys that have a lot of amps under your belt, do you prefer the clam shell type connector on a socket or the old fork type?

I'm trying to figure out what is the best type for longevity and performance.
Which style holds tension the best?

Fork type
[img:507:336]http://www.turretboards.com/images/PROD ... ertype.JPG[/img]

Clam shell type
[img:498:338]http://www.turretboards.com/images/PROD ... chunky.JPG[/img]

Also I have read that sometimes ceramic sockets can promote microphonics of a tube do to the rigidity of the material.

I usually use the black plastic type (Amphenol?) or brown/ tan micalex (Cinch?)sockets.

Just curious about the pin type.

[Cliff Schecht]

A DRRI just came across my bench with an issue much worse than Firestorm's. The amp goes into a crazy screeching distortion. The vibrato circuit seems to kick on randomly even with no footswitch and the reverb knob squeals like a piggy when you turn it up past a few clicks, with or without the reverb installed. Seems to be a common issue.. Anybody fixed a similar problem before?

[Cliff Schecht]

So after digging for quite a while I found the troublemaker in this amp. It's a weird one though. With the stock choke in the amp and either volume past 2 or 3, the amp chirps as I hit a note decently hard. When I short the choke, the noises go away and the amp sounds fine. When I clipped in another choke, the amp chirped again just like before. When I removed that choke and put in a 150 Ohm resistor, it worked fine. I'm thinking about leaving in that 150 Ohm resistor but I've never had an amp that only freaks out with the choke installed! The only thing inline with the choke is the two connectors to the board and the solder joints look fine there..

[Reeltarded]

wtg on finding that

Everything for two weeks hasn't made any sense. I have two problem amps here that make me question physics!

Off topic completely, where can I buy replacement pots as the ones that come in these later model Fenders? I have a Twin that rolled into a cobblestone street face down. These pots are not stabilized by extra legs on a cage. Just the three terminals.

[Cliff Schecht]

Mouser probably. You might have to dig to find out who made them or find something similar that will fit. Or use a very small pot and connect the solder lugs with wires.

Yeah this amp is a real sumabitch. It's one of the weirdest ones I've encountered. If I replace the choke with a resistor of nearly the same value the problem nearly goes away. Light squeal with reverb cranked, nothing unusual for Fender DRs. When I short the choke completely I have no problems whatsoever. Crank everything, everything sounds great. I already tried all of the troubleshooting tricks I know and I've definitely isolated the problem but I can't for the life of me figure out what part(s) are causing the issue. I usually don't consider an amp fixed unless I can point out a definite issue and can say for sure that my fix has repaired said issue. I might try swapping out a few parts in the HV circuit to see if I can find a troublemaker (I'm thinking the main filter cap or the screen filtering cap, one of the guys connected to the choke!).

[Firestorm]

On my problem DRRI, the screen filter was beginning to leak electrolyte, so maybe something there. (Odd considering the relatively young age.) The main filter in the DRRI is kind of unusual; if one of the voltage divider resistors goes haywire, there could be truly odd results. Maybe check that.

[Cliff Schecht]

Exactlt what I was thinking. Did you notice the goofiness they did on the first filter cap? 220uF 100V cap in series with a 47uF 500V cap with adjusted bleeding resistors. Very goofy thing they did. I tried shorting the bleeding resistor on the 220uF cap to take it out of the circuit, didn't fix anything. Will try the screen cap next, since this feeds both the vibrato, reverb and PI share this point and all three circuits are acting up.

[Firestorm]

Some of the grounds seem to go through the pot PCB via the ribbon cables. The solder joints on the ribbon cables don't always take. On the one I had, one of those was bad. You have to look close to see them, and maybe try to wiggle each one with a probe.

[Cliff Schecht]

Oh yeah, forgot to mention. Woke up this morning and looked at the screen cap. Piece of shit was leaking. As I swapped the cap out I noticed the IC (R) label was different than the one I was putting in. Looked either fake or like a cheaper variant. The one I bought came from AES and I've had no problems with IC caps in the past, so I think Fender either got a bad batch or got shafted over in China and didn't even notice it. Either way, got it all working and back in one piece. Even cooler was the guy I work for said I charged to little for the work and took my '52 AVRI Tele to setup and intonate. If there is one thing this guy does well its making guitars play in tune. Can't wait to get some humbuckers in that Tele and finally start gigging it again!

[frostbite]

Hi to All - I have been reading this thread with interest and some very good discussion regarding the DRRI issues ...

I hopefully am going to solve the issues wirh my DRRI, as I am going to install a point to point board in it along with basically a full rebuild and fresh solder using the old fashioned 60/40 resin core solder .... I don't like or trust the new lead free solder rubbish that is being used these days ....

It is going to cost a few dollars to do the rebuild but seeing as the genuine DR's are not easy to find here in Australia, I don't mind spending the dollars on the DRRI to bring it back to original specs ... and besides it will give me a greater understanding of the workings .....

I have had recent issues with my amp - same as described by a few here, with the volume either dropping out altogether or dropping to a very low level .... I have tried a few things and nothing has worked so far - My parts are coming from Marsh Amplification and should be here in a few weeks for the rebuild - meantime I have bought some new Japanese made 8 pin Octal bases to try - they have to be installed anyway, and see if that is the problem...

I will keep an eye on this forum and see what develops with the DRRI issues and give a report on my findings as well and keep things updated with the rebuild as it progresses - maybe even some piccys as well ...

Cheers to All - Great forum - Very informative - Thanks to all the contributors ...

Regards -
Greg - alias "frostbite"
COOMA NSW
Australia.

[Jana]

Tom,
I prefer the "clamshell" type. The fork type are okay for a little while but then, after a few wiggles and insertions, the forks spread and can make intermittent contact. Yes, one can "retension" the sockets but it is a hassle. I know, a lot of vintage amps have been built with the fork type. I also know, from experience, a lot of problems they can cause.

The ones that diagrammatiks posted a link too look really nice. That's what I would use if I didn't have a stash of pin grippy sockets. Yeah, they are expensive--but so is a tube if it looses grid contact and goes redplating due to lack of bias.

[Colossal]

I hopefully am going to solve the issues with my DRRI, as I am going to install a point to point board in it along with basically a full rebuild and fresh solder using the old fashioned 60/40 resin core solder

Cheers Greg, that is a great plan