Fresh blood

[otisboss 17]

Hey all,

 

I have been hanging on to a TFM-25 as a first owner with the original box and stryofoam (much to wife's discontent ) for past 30 years - Got a kit for rebuilding from eBay that  likely spent too much on.  Gonna replace the caps and do the 4/15/92 service bulletin upgrade. Wish me luck!

 

Cool site - read a couple cool threads already!

 

Brian

[wrf 4,980]

Welcome to the site @otisboss.  I assume you have found our library.  There is an excellent service manual for the TFM-25 there.

 

The service bulletin understates the potential damage on the PCB.  In extreme cases, the board under the resistors and transistors targeted by the service bulletin can become severely burned and even damage the traces on the back of the board.  Be careful.  It's easy to cause further damage when removing components in this area.  Inspect the back of the board carefully for overheated solder joints and weak traces.

 

Is the amplifier currently operating properly?  If not, I would recommend doing a bit of diagnostic work BEFORE the recap and service bulletin work.  It's always good to know what's broken before unleashing a bunch of parts on an amp.  That way you can set expectations. Rarely does a shotgun of new parts solve an unknown problem in an amp.

 

Even if the amp is working properly, I would recommend a quick health check prior to replacing the parts.  Power supply voltages, bias setting, DC offset etc.  That way if there are problems later you know if the new parts caused the problem.

 

Good luck.  The TFM-25 is a fine amplifier and well worth the updates.

[otisboss 17]

Thanks wrf.  I got it in 1989 when heading off to college (Marquette University) playing through some old AR-35BXs that have been lost to time.  I loved the speed and punch of that set up.  And it got loud!  Later, the TFM25 was weak and or cutting out in one channel and that is when it got boxed.  It is in mint condition externally, but obviously I will need to look carefully inside.  I have some experience with electronics, pretty nifty with a soldering iron, and enough sense to be careful of dangerous voltages.  I did intend a cover off inspection first, then to fire it up with a dim bulb test and see if anything appears grossly off.  I will definitely be checking those items you mentioned above. 

 

I looked through the TFM-25 library at many of the issues - service 2 resistor and transistor replacement, comments on capacitor replacement (and failures to discharge caps!), and input regarding replacement of output relays.

 

Unfortunately, I did not do all this research before sourcing a "rebuild kit" from HiFiAudio on ebay - it includes a near-full cap set, several transistors, and a number of diodes, . . . but not the resistors for service bulletin-2.  Also, seems to be lacking caps C451 and C510.  Instructions for the capacitors is fine, but absent for the transistors or diodes.  AFTER researching, I see that Les (@circuits&concepts) has a power supply capacitor rebuild kit - now I am wondering the quality of components I purchased (kicking myself).

 

I did see Jazzman's list of parts for the TFM-25 rebuild - excellent resource, thanks!

 

So any info on HifiAudio's TFM-25 kit, anybody?  I do see some Chemicon and Nichicon smaller caps, but not clear if the larger ones are real or knock-offs?  Any advice for identification, testing, ???  (Can't post pics quite yet, too new!)

Since I have yet to even start, would it be worth sourcing those 6 power supply caps to be sure??? 

 

https://www.ebay.com/itm/222548677988?hash=item33d0ef5564:g:S1wAAOSwjk9ZRGza&amdata=enc%3AAQAIAAAA4L2l75jzTqzkVA5oZTwh8wDvHjNVTWvRk5K6cen%2BPAxYDPGbXj9fASMAhY32Wy%2BVV9nUeoyCGiCoguuWJ5xPpeuACP9t0XMzJu1xcVLcsH90T98i%2B58M5QJymVcNrb9Dph1fCgEIL4vbPijkDuArtUfnBG6w1Ef2%2BaAP1ZUm2Rm%2BLVkGqiehZ0Ix9jykr7cYnTzLQ%2FV65045zApgnmULptnySATCydDAPCvGT0xT76GYkl%2FItWzyF82T%2F1CQDjPrdYxmBv6LIphRdu4ja0cqnc3KzDRLxXQzAiZbQhYF6lpe|tkp%3ABk9SR76Lgb-aYw

 

Also, when replacing binding posts and/or RCAs, any preferred manufacturer?

 

If there are obvious 'upgrades' for these amps it would be great to have it spelled out clearly rather than strewn over a multitude threads 'to discover'  - For example, I have a couple cars that lend themselves to upgrade paths and there are some nicely codified threads on EvoM.net and S2k.com that review typical upgrade path - instead of wider tires, 18" rims, improved turbos, discussing benefits and tradeoffs expected with the upgrade in question; Maybe I missed a similar 'recipe' for the TFM-25 in my initial foray.  If planning for upgrading performance (not just spending $ on fancier parts) what replacement caps would be recommended (and the like) - saw this for a tube amp I'm building, basic set, higher level, top tier. 

 

The future paired speaker would be a modest KEF floorstander, yet unpurchased.  I have some various bookshelf speakers to play via digital and analog sources in the meantime.

 

Thanks again any and all - happy to get in touch with my OCCD!!!

 

Brian

[BobTFM35 2,774]

@otisboss Welcome to the site!! You have joined and come to the best site for Carver and other Audio gear information bar none.

 

Good Luck on the TFM-25 repair, and after that I'm sure that other Carver Gear will find its way into your rack.

[Cring08 246]

Welcome !

 

[xavionics 2,091]

Welcome to the site Brian! 
 

Les @Circuits & Concepts is a member here and a valuable source for parts. 
I’ve purchased several power supply kits from him a and have been very happy with them.

 

I did a couple TFM-25 rebuilds a few years ago, chronicled here:

There is a pic of all the caps I removed. And pics of the “upgrade” parts I.e. binding posts, etc.

The pic of the removed caps just happens to show the values.

 

When you dive into this, start a new thread.

Add pics, chronicle your work, ask for help if needed. 
You’re in good company here… 😎

 

 

 

[wrf 4,980]

@otisboss

 

Wow.  So much to unpack.

 

@jazzman53 is a huge fan of the TFM-25.  His posts are excellent and can be used as good guidance.

 

I wouldn't be too worried about knockoff caps.  Nichicon and Chemcon are good brands.  

 

I would hold off on shot gunning all the parts you have into the amp.  I'm a big fan of first diagnosing and fixing any problems before carpet bombing the amp with new parts.

 

Truth be told, the binding posts and RCA connectors in the TFM-25 amp are fine.  Changing them may look nicer and feel better, but unless there are problems, the stock components should be good.

 

@Circuits & Concepts is an excellent and reputable source of packaged components.  Mouser and Digikey are good sources for individual components.

 

So sorry that the upgrade information is scattered.  This might be an opportunity for you to create a consolidated thread for others.  We are an all volunteer site, supported by donations.  Sometimes folks get fired up and post excellent DIY tutorials.  Sometimes somebody gets motivated and consolidates fragmented info.  It all depends on the membership.  This is your chance to create a timeless contribution to the Carver community.

 

Depending on what you find after an initial test and survey of your amp, you may want to consider sending it to a pro.  It's not a bad starter amp to learn on, but you can dig a big hole if you are not careful.  We are usually very responsive to questions you may have and can help, but diagnosing an amp via photos and messages only goes so far.  Greg, the head honcho of Nelion idoes excellent refurb work.  You can contact him directly here @Nahash5150 or via his Sound Room and even his web site.  nelionaudio.com

 

 

Good luck and keep up posted.

[BobTFM35 2,774]

I can attest to the quality of the Nelion Audio @Nahash5150 work, It is top notch. My son and I have entrusted him with several prized pieces of equipment. They have come back to us ready for the task of some great performance.

 

Here is his listing for the TFM-25/24 restore, and his warranty tells you volumes about the quality of his work.

 

https://nelionaudio.com/index.php?/services.html/carver/carver-amplifiers/carver-tfm-2524-restore-r9/

 

Good luck.

[Receiver2000 4,112]

Welcome otisboss!!! My wife is none to pleased with my equipment boxes either. 

[Kurt 2,946]

Welcome to the Carver SIte!

[AndrewJohn 10,502]

Welcome to TheCarveSite, @otisboss  So glad you found us.  

 

Keep posting on your journey with your amp.  Looking forward to the end outcome!

[Ar9Jim 6,514]

Welcome to TCS sir..

[Zenith4me 1,485]

Welcome to TCS!

[otisboss 17]

Thanks for the support!!!

 

Currently awaiting parts from Digi-Key to complete the service bulletin repair. I did briefly look inside and see the board discoloration as anticipated and addressed in the service bulletin. Wasn’t quite ready to get down to testing at that time. I’ll do a separate thread and can hopefully upload pics.
 

I do intend to test and hopefully address any issues before cap replacement and service bulletin repair. Appreciate the references for technicians in case it is beyond my scope. 👍

 

B

[Sk1Bum 11,513]

2 hours ago, otisboss said:

I’ll do a separate thread and can hopefully upload pics.

 

You can upload pics now that you've reached Novice status.