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Sticking Caps in Marantz 2216b

writesds

writesds

New Member
I'm new so thanks in advance for your help. First, any advice on removing caps which appear to be stuck to the board? (See photo) I desoldered all pins and these large 4700 caps on the output board are not budging at all.

Second, I picked this receiver up with a blown transistor. The guy shorted the speaker wire with power. I removed the bad one, isolated and checked the other transistors, diodes in the circuit, etc and everthing except that one transistor seems to be ok. Only that channel had static when tested and the other side seemed to play ok. Any suggestions on other potential failures which should be considered with this repair? Any thoughts on the best supplier for these transistors and those caps?
 

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Welcome to AK! thanks for the pics. Probably glued down caps. Pics are deceiving for that cap 'bulge'. DMM the b+ b- rails v and if okay maybe caps are still good. Transistors.. okay to replace the one but I just don't know if balancing the pairs if needed will be better? would be good if you had a scope on it. If no response 'joy' might repost on the marantz forum. Thanksgiving week so who knows who will reply.

third speaker wire short this week, I think.
bink :D
 
Marantz was very liberal with their glue and it is hard to remove. Best tip I have seen for dealing with this on large caps is - after desoldering completely, cut the plastic liner on the outside of the can from top to bottom and open it up. The cap should lift out. Then the plastic casing will peel off of the glue leaving you with a pretty good job of removing the glue. Acetone and 91% isopropyl alcohol will VERY slowly loosen it up and let you scrape it off, or you can carefully scrape with something sharp like sharp wood chisel. The stuff is brittle as it sits and will come off in chunks. Just don't want to gouge the board when doing your scraping. This method puts the least amount of stress on the board in my experience.
 
Neat trick. Steven, even though those large caps tested good, do you recommend replacing them with the others? Everything in this amp appears to be original.
 
I'm far from an expert. I have rebuilt 8 or 9 Marantz receivers now, and I follow the advice of a lot of Marantz experts and replace all of the electrolytic caps including the filter or coupling caps. If you spend a lot of time seeing this question debated, you will see there is no consensus on whether to proactively replace electrolytics or not. I have personally heard the difference in each unit I have rebuilt. I listen after every board upgrade, and almost always, I hear better sound after each one. These electrolytics are 40 years old now, and that is well past the design life for most of them. It helps that it's just a lot of fun to me to do this work board by board. If you have questions about your unit, I recommend that you post them in the Marantz forum of AK. There are a large number of very experienced folks there that are more than willing to give you their opinions and advice. Just be careful. This can be addicting, and you may find yourself with a room full of receivers before you are done. :rflmao: Good luck! :thumbsup:
Steve
 
I did notice in your pics the disconnected but still soldered in transistors on the heat sink I doubt the large caps are an issue and as mentioned scope would be good. I also notice output transistors disconnected from the heat sink. I hope not testing that way.
 
Check all components in that channel, even the variable resistor r19 as they sometimes look ok but get fried. look out for bad resistors and diodes.
 
Definitely becoming addicted again after being away from it for years. I do plan on doing all the caps and will check those resistors, too. As for those disconnected transistors, already ordered all four. The missing one was burned up. This won't see power until they are replaced and reassembled. Good point about that heat sync. Common problem I bet. Even ordered some Dow 340 heat sync compound.
 
A burned output transistor often means a bad component or components upstream. Be sure to use a DBT the first time you fire it up with the new outputs or you could instantly fry one or more of them.
 
I change the four transistors against the heat sink and a few bad caps. Everything else tested OK, even those suspect filter caps. Here's a photo with the DBT. Now, I have make a decision about recapping.
 

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