Overview

I have a C-16 in the stack waiting to be repaired and I haven't opened it up yet, so I'm curious as to what made this one so difficult? Any unusual parts that will be difficult to track down?

Tests great too!

C-16 (this was torture!)

Bad bad bad! Thankfully, only a fuse and a pair if output transistors are bad. I replaced the whole stage though. All back together! New meter bulb and meter check, the cover is back on, and now a bit of faceplate cleanup Before: After:

Not really typical. They fail as a result of a few things like a failed TDC, bad regulation (bad caps), cracked solder joints, abuse, etc. The problem is that Sunfires don't shut down from a fault - they just mute. So power stays active during a failure until it becomes a light show. The fuses rarely save the day...they only prevent complete meltdown (hopefully).

Positive energy coming your way!!!

Yeah - 20 hours is at the low end of time. I will not make any money on this. I have bills like anyone else - it's not about making money, it's about being responsible with it. I have to be very careful what work I take. If a project gets too demanding of my attention, other clients suffer. And I certainly do not want a shop full of unfinished projects that are over a year or two old. I told myself I would not do that... Anyway, fxbill is a great salesman. Looks like I'm doing it. For team Carversite...here we go...

I agree with @BobTFM35 regarding all the parts. The question in my mind would be the labor. There would be a *lot* of it. Your quote (from the customer, I assume) used the word "just". That would set off some alarms in my mind as it would indicate they are thinking it's a simple job that might take a couple of hours. I don't work very fast, but if I was estimating labor for the project I think I'd be at least 20 hours. Would the customer be OK with that bill? I bet they'd be shocked when they heard the number. Still, it looks like it would be a fun project. I have a soft spot in my heart for that vintage point-to-point wiring. It brings back memories of old Dynaco kits.

Greg @Nahash5150 I don't know the back story on why this amp is on your bench. Lets say, its not a customer, but something that you sourced for your own use. If it was for a customer, I might have written the following differently. I did a little research on this amp and I've come to this conclusion. I just hope that I can explain it clearly. First the going price for this model, depending on the condition is maybe 3500 to 5000 (correct me if I'm wrong). That was the asking prices on ebay that I viewed. For discussion purposes lets say I can flip it for $4000.00 and I spend no more than 1200 for parts, don't know the bench time required so I can't factor that in, but it could still come out to be a nice profit. One of my first decisions is on availability of spare parts. You have a very nice Chrome chassis to work with. The vendor that I found for that chassis (and possibly the same one that the chassis was sourced from) also has some very nice reproduction pieces, such as the decals for the transformer covers and either a silver or gold badge 240 badge. For you sourcing the tube sockets, correct wire color and size would be no problem. The other sockets or holders for the metal caps (or whatever they are) I feel that you have the abilities to source them. The pots, depending on their condition, might take some reconditioning. Might need to see if replacements are available. I do know that for the dynaco amps there are a few vendors offering parts for restoration so maybe this is the case for the 240 amp. No doubt you have the wiring diagram for this unit so that would be a great source of encouragement to start with. I might start placing as much on the new chassis as possible such as the tube sockets, pots, and speaker terminal strips, some preliminary wiring with lengths long enough to be later adjusted, thus using the original chassis and schematic as a guide. I do know that you not only have the correct equipment but also the knowledge and experience to tackle this endeavor with a systematic approach, and that in Itself gives it a way better chance for success. Enough encouragement? You have this.

Correction - FxBill worked on it and he says it works...so...that is a bonus!

NEW! No Brainer! The new one looks so sweet!

If it were my decision I wouldn't touch it; too many booger solders and shade tree work going on...

I may or may not do this...I'm having second thoughts. 'The guts just come out and go right into the new chassis...' Ha!!!!! It wouldn't be too bad if the transformers could just 'unplug' but they don't. Their wires travel everywhere...and that's real problem. There's no room for error - the wire lengths are precise. 3 transformers - each with 8 to 20 wires. All rivets have to be drilled out. All RCA jacks need to be replaced. The thing needs a severe cleaning and polishing. And the worst part - HUMAN HANDS. Previously worked on and it doesn't work. Worst problem ever. I'll need encouragement because I really want to say NO.

just curious, is there a typical reason for this common failure? Any prevention possible? Or does it fall into the two buckets of a) user abuse and/or b) aging or low-quality original components? Thanks for sharing this project. Looking forward to watching the whole thing!

Tearing it down: And of course it has a blown channel...it's rare to work on a CG and it NOT have a blown channel.

I use these: https://www.mouser.com/ProductDetail/REAN/NYS367-0?qs=R5cXQUTKuHU8XkQYanQZXg%3D%3D The number after the dash selects the color. The above is black.

Nice! I have a DH500 and the RCA inputs are deteriorating on the inside. Occasionally I have to mess with the cables. I think as stage 1, I will give the insides a bit a of a clean and replace the RCA jacks. Which RCA jacks did you use for this one and did you have to open up the holes in the chassis at all? Thanks in advance. Grace and peace, Ben

Wow, that is so weird. I responded to the same thread when Jim offered the discount on the Guttenberg unit. Though, when I look back at my emails with Jim, while I did ask for the Guttenburg unit, he never came right out and said that's the one he was sending me. So it's entirely possible I got something else. I assumed the one I received was the review unit, though. Because, 1) I got the $500 discount and 2) when the Amp arrived, the tubes were already installed and a screw on the back plate was not tightened all the way, as if someone had opened it up, looked inside and didn't tighten all the screws back up. So, it seemed "used" to me. Also the box it came in had been taped closed, reopened and retaped. I guess it doesn't matter. The main reason I mentioned that I had the review unit was just to make sure folks had all the info when making diagnosis/comparisons and offer up one reason why my unit may have some differences. Now you have me even more worried that I have a ticking time bomb in my bias meter!

That's about roughly when I started having trouble with mine, around 300 hours or so. It started with a loud "PoP" shortly after power up, I was in the other room and heard it quite loudly through the speaker(s.) Amp still sounding fine so shrugged it off. A couple days later noticed the meter was only reading 20ma or so and when I tried to re-adjust the bias it would max out at around 55ma? It's a little funny, I've seen you mention before that you had the "review" amplifier- I wonder which one of us actually got that amp as I supposedly bought that amp too. I don't really care if I'm being honest I just jumped after it because of the $500 discount that was offered at the time, which he ended up extending to all new amp sales anyway. Jesse

I wanted to say thank you for taking the time to look at and fix my amplifier- I've had it back in the system for a few days now and it appears to be working perfectly again. As much as I enjoy the 275 amplifier the 285 is head and shoulders better IMO; it has the warmth and tubyness while at the same time solid state like bass and clarity and good high end which by comparison seems pretty rolled off on the 275. Anyway, thank you for stepping up and offering service for this great amp- while frustrating that @Ar9Jim Jim Clark ducked out it is understandable and I don't harbor any hard feelings towards the guy. Jesse

Just a data point for you... I checked my bias meter. It's steady at 75mA at idle and seems to move just fine while playing. I have had my 285 since May of last year. I'm probably putting 4-5 hours per week on it, I'd say. So, close to 300 total hours, i'd say (also this is the unit that Steve Guttenberg used for his review, so, it had some hours on it before I got it).

Thanks @Nahash5150. That's helpful. I've logged a lot of hours on my 285....haven't noticed any issues. I'll check the current bias reading and let y'all know.

The bias should stay between 50mA and 150mA at idle after 10 minutes of warm up. If you've chosen your sweet spot, say 90mA (because that's mine), then it shouldn't change. If it does by more than a few mA, then it could indicate a problem, especially if it won't adjust properly or keeps falling out of your sweet spot. We aren't taking over the warranty. We are just willing to service these units and do our best to support them, unofficially, because right now, there is no official support. I'm sorry I don't know the exact origin of the trouble. I just know that it seems to be related to time, nothing else.

Related question...... is Nelion taking over the warranty work from Jim Clark?... I know he closed up his shop, got a new job and has been real busy. But, on his way out, he did say the warranty's would be honored.

I haven't touched the bias adjustment on mine. I was advised I may never need to do so. How would I know if I have an issue?