DIY Audio Projects Forum
 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

DIY Audio Projects Forum

Welcome to the DIY Audio Projects Message Forum. Use these forums to discuss Hi-Fi audio and to share your DIY Audio Projects. Registration is free and required to post messages and view the file attachments. Registration will only take a minute and registered users do not see any advertisements. After you have completed the online registration process, check your email (including spam/junk folder) for the verification email to activate your account. New members are under moderation - so your posts will not be visible until approved by a moderator. See the Read Me 1st, Forum RULES and Forum FAQ to get started on the forum.

It is currently 05 Mar 2021, 21:21

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 7 posts ] 
Author Message
PostPosted: 08 Jan 2021, 20:45 
Offline

Joined: 23 Mar 2020, 11:45
Posts: 3
I put together a Gainclone years ago using the Texas Instruments LM3875 and some toroidal transformers, etc.. I enjoyed it many years, but unfortunately, it was not spared during a flood when I failed to secure it, unlike many other less valuable items. Some time has passed since then, but I'd like to see what might be salvaged from it. Any tips on how to go forward with this will be much appreciated.


Top
 Profile  
 
PostPosted: 19 Feb 2021, 22:28 
Offline

Joined: 09 Oct 2012, 19:43
Posts: 376
Location: Vancouver Canada
So you have the amps then but they are just water damaged? Or are they lost altogether? The LM3875 is a discontinued IC but
Avnet Europe has 500 in stock and Element 14 has 69 in stock both asking around $10.00 each.

If you still have them, some pictures are always 100% helpful in assessing damage and a direction to focus on to renew or replace. Help us to see and maybe you will be rewarded.

There is now a world of selection when it comes to the gainclone amps. Class-D and now Class-T is a popular design. Amps like the LM3875 were pioneers for their time but times change and the selection now is vast by comparison.


Top
 Profile  
 
PostPosted: 19 Feb 2021, 22:56 
Offline

Joined: 23 Mar 2020, 11:45
Posts: 3
Thanks for the reply. Here are some pics:

Attachment:
20210219_213607.jpg

Attachment:
20210219_213601.jpg

Attachment:
20210219_213557.jpg

Attachment:
20210219_213547.jpg


I couldn't tell anything by looking at them myself. There were originally another couple of transformers in the box that are not there now, for some reason I cannot remember. There is a mud-dauber nest shown in one of the pictures. No surprise around here for something sitting in the garage. I don't believe it was there when I did my initial test. Which components would be most likely to survive a flood. I'd think that the IC's would be OK, caps likely not, but I have no experience with this.

I already broke down and ordered a Hypex NC250MP and am just waiting for the box to put it in. I was too cheap to order 2 of them to recreate my initial setup with the gainclone that had an active crossover with each driver having a dedicated amp.

I'd still be interested in reviving the GC if it's not too much hassle, etc.


This post has a file attachment. Please login or register to access it. Only Registered Members may view attached files.



Top
 Profile  
 
PostPosted: 20 Feb 2021, 23:49 
Offline

Joined: 09 Oct 2012, 19:43
Posts: 376
Location: Vancouver Canada
First off pay special attention to the AC input side of things. Fuse, switch, line cord etc. Don't want any mishaps in that area. In
the pics it looks all gungy but not that bad.
Water ingress would be worst in places like the blue Maretts (wire ties). Take em off and re-strip then new ties. That dual pot is going to be gone. If not now, shortly soon after use from lack of grease on the wiper tracks. Luckly they are common. The diodes, resistors, transistors, all the wire solder solder joints should be ok. Wiggle parts (res, caps, etc) to make sure they don't just break apart like they do if heated too much.
Caps, well the electrolytic ones have fluid in them that is being kept in, so, water would be kept out. Look for wire corrosion on
wire, wire connections, and wire coming out of parts. That is all the parts at the point of entry.
The wire junction spots (soldered and bolted) that may have conductive contamination joining things/parts that should NOT be.
Also attention to the isolation washers under the amp-tabs isolating them from the heat-sink they are bolted to. Basically look for places shorts may occur in areas that should have no connection at all. That is what will throw an amp into oscillation and self destruct.
Taking a toothbrush to all metal leads would be comforting. It would be good since it is a SS amp a variac would allow gradual power to be applied. A dim bulb tester is just an incandescent lamp in series with the AC line cord so if any thing shorts out the lamp will glow instead of the amp taking flight. Speaking of taking flight, make sure those flying components are not touching.


Top
 Profile  
 
PostPosted: 21 Feb 2021, 00:02 
Offline

Joined: 09 Oct 2012, 19:43
Posts: 376
Location: Vancouver Canada
If you have a meter you could disconnect the power supply and test it first to sure that part is
working. Then possibly test one channel at a time as is IMO what most of us do when putting
a new amp together.
Just some input. Lots there but mostly common sense stuff. And yes if it has sat for some time
it would be wise to change the caps. They are cheep enough now days and the re-soldering
won't hurt.
One last thing, turn that PCB over and give it a scrub as well. Get the mud dauber's poop out.
Let us know how you make out.


Top
 Profile  
 
PostPosted: 22 Feb 2021, 11:46 
Offline
User avatar

Joined: 04 Nov 2013, 21:18
Posts: 95
Location: Florida
you could do what I do...put the whole thing in a waste basket, use a long extension cord plugged into an outlet controlled by a wall switch...place the waste basket at the far end of the room and switch the flip. If it goes bad, its already in the garbage.

_________________
Are we not men?


Top
 Profile  
 
PostPosted: 22 Feb 2021, 19:47 
Offline

Joined: 23 Mar 2020, 11:45
Posts: 3
Thanks for the guidance, Laurie. I'll be delayed getting back to it, but I'll post what I find when I do.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 7 posts ] 

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 9 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
DIY Tube Projects :: DIY Tube Amp Kits :: DIY Speaker Projects :: DIY Solid State Projects :: DIY IC / Op-amp Projects :: DIY Phono Projects :: DIY Cable Projects :: Hi-Fi Audio Schematics
© diyAudioProjects.com - Terms of Service - Privacy Policy