Stereomour Build

[marantzfan]

Well, I will be joining the bottlehead owners club soon, I ordered a Stereomour last week and am getting excited about the upcoming build.  As always, that means I have some questions.  

1. What kind of paint works best for the transformer end bells?
2. Would Jantzen Z-Series capacitors be a noticeable upgrade from the stock Solens caps?
3. Any suggestions on stain for the wood frame to match the color of a Linn LP12 Afromasia plinth?

I'm sure once the kit gets here and I get started there will be much more to come.  

Heck, I haven't even gotten started yet and I'm already looking at the Eros.  

 

[Paul Birkeland]

I like to paint or powder coat the transformer covers with a finish that is not smooth, as those parts tend to take a bit of a beating, and a textured or wrinkled finish takes the abuse better.

I've used Jantzen caps plenty of times in various builds, though mostly because they tend to have higher voltage ratings.  From a construction point, both the Jantzens and the Solens are metalized polypropylene caps (doesn't mean they don't sound different).

Stain matching is a pain, I'd buy the closest 3-4 cans at your local big box HW store, then test them on the back of one of the base pieces.

 

[marantzfan]

Ok, my kit came in two days ago and last night I got started on it.  After about 2.5 hours I'm up to page 32 which is where it's time to mount the PT, so now it's time to figure out what I'm doing with the paint/powder coat so I can move forward. 

I think I am going to go with gloss black paint as I don't really want to wait to get to get it powder coated although I do think that would be the best route.  My question for now is how do you paint the casings on the chokes next to the PT?  Do they come off somehow or do you just mask around them?

 

[Doc B]

Don't try to take them apart. Just mask them off.

 

[marantzfan]

Thats kind of what I figured just looking at it but I wanted to make sure.  Looks like I should do some sanding first then primer and paint. 

 

[Doc B]

Sometimes the varnish that is used on the transformers gets a little drippy on top. I use a rag and some acetone and rub the top vigorously. That will usually clean the varnish off and leave a clean surface.

 

[marantzfan]

Awesome, that will make things alot easier.  Thanks again.  Time to get painting tonight after work. 

 

[marantzfan]

Well, I got it all put together and my voltage checks were good so I powered up and listened to it last night.  This amplifier sounds really nice but for some reason the left channel will cut out, almost like its not making a good connection with the socket.  If I turn the amplifier off and reposition the tube and turn it back on the left channel will play for a while and then cut out again. 

What's going on here?

 

[Doc B]

Rewet the solder joints around that socket.

 

[marantzfan]

Roger that.  I'll do that tonight and report back. 

BTW, not sure if I mentioned it earlier but this kit was an absolute pleasure to put together. 

 

[marantzfan]

Hmmm...

Well I rewet all joints at the socket and around it.  BUT, I don't think I properly diagnosed the problem before.  Although the first time it was the left channel that would cut out, now it seems that either the left or right will cut out.  If I touch the metal plate both channels play just fine.  Grounding issue?

BTW, here is a picture of it.

 

[Doc B]

Check the connections from the 12AT7 to the volume control, and from the volume control to the selector switch. Sounds like it might be a missed or cold solder joint.
By the way, looks really nice!

 

[marantzfan]

I have checked and reflowed every joint at the 12at7, the volume control, the selector switch, the left 2A3 socket, actually pretty much everything on the left side.  The problem remains in fact it seems to have gotten worse.  I don't know what to do now.

 

[Paul Birkeland]

Can you post a shot of the underside of the chassis?

So you get 0 sound, then if you touch the plate everything comes back?

When you touch the plate, are you tapping on it, or just ever so gently touching it with your finger? (Is there a difference between the two?)

 

[marantzfan]

The right channel will cut in and out; if I touch the top plate (with a little pressure) it will bring it back when it cuts out.  The left channel now just seems to be out.

 

[2wo]

Does it do it with all of the inputs? See if it makes a difference if you touch the selector switch or the volume pot. Check the RCA jacks for shorts or a bad connection. Put a temp jumper across the grid stopper.  If that doesn't do it we can try running a direct  jumper from one of the RCA jacks to the input grid of the 12AU7...John       

 

[Paul Joppa]

From the description, it seems it's a connection that is easily disturbed mechanically. That could be a bad solder joint (covered with solder, looks good, but solder is touching the wire instead of wetting it) as has been said. We say that all the time because it's most often the problem. But other possibilities are poor switch or socket connections, for example.

Does the problem occur with all three inputs? That's a test of the selector switch.

Another one that has come up recently on the forum somewhere is wires that get nicked when stripping, then break later right at the end of the insulation. It's very hard to see, and the insulation holds the parts close together so that slight mechanical shocks can make or break the connection. Usually wiggling each wire one at a time will make this one obvious ...

Another one is a mechanical connection that was not actually soldered.

 

[marantzfan]

I've done some poking around and I don't see anything.  I will try the different inputs and also retest voltages and report back. 

 

[marantzfan]

Well, tried the other inputs and the problem is still the same.  Touching either the volume or selctor switch does nothing but tapping on the top plate brings the left channel back on for a minute or less (random).

I'm guessing the volume knob?  Which is the left channel, top or bottom?

 

[Paul Joppa]

I should have mentioned the chopstick test as well - it's clumsy and dangerous voltages are exposed, but sometimes it helps when nothing else does.