Threshold 400A Looking for advice on restoration - Page 2

Redwingnine · 5th November 2010, 10:03 PM

Quote:

Originally Posted by Zen Mod

I will not loose a sleep regarding new outputs ; and that after more than 20 years of service work

I don't have that - missing - page , but I think that you have more than enough information later in document

That was my thought as well. It sounds outstanding as is right now!

I reckon you are right. Should be able to work out the bias procedure with what you provided. Again, much thanks!

Redwingnine · 6th November 2010, 07:58 PM

Well, the most recent email I received from the Threshold repair guru strongly suggested that the output devices be replaced.

Given that advice, was lookig at replacing the old devices with the following:

ON MJ21193/MJ21194

If I read other threads correctly on DIY, this should be a drop im for the 400A, and provide better max voltage/current performance.

Anybody actually used these on a 400A? If so, how did it work out?

Zen Mod · 6th November 2010, 08:11 PM

OK

if Guru sez , then you must obey

if I can recollect my memory - there was a thread started few years ago by one bitchy guy , and I just couldn't understand how and why boyz (including Papa ) gave him so much help and information for his T. repair

I think that there you'll find some more info about best outputs

but - if Guru already give you advice - listen to him

when you don't have experience ( in exact matter) of your own - you must trust someone .

Redwingnine · 6th November 2010, 08:25 PM

Quote:

Originally Posted by Zen Mod

OK

if Guru sez , then you must obey

if I can recollect my memory - there was a thread started few years ago by one bitchy guy , and I just couldn't understand how and why boyz (including Papa ) gave him so much help and information for his T. repair

I think that there you'll find some more info about best outputs

but - if Guru already give you advice - listen to him

when you don't have experience ( in exact matter) of your own - you must trust someone .

Zen, since it was the guru (Jon S.) who advised me on this, as you said, must trust someone. Since I really enjoy the sound from this amp, want to make sure it's done right.

I found that thread you mentioned, and yes, much heartache. I found another thread where Papa suggested these devices (which I think are the smae ones Threshold used for their amps in the 80s and early 90s).

Zen Mod · 6th November 2010, 08:33 PM

so - dilemma solved

Redwingnine · 9th November 2010, 12:38 AM

I'm ordering a rebuild kit from Jon S. at Vintageamprepair (thanks, Jon!). Also found a guy who will re-anodyze the faceplate. Will post pics once done.

wkjeffers · 23rd November 2010, 03:24 AM

I would really like to know who you found for the re-anodyzing.....I just bought one that could use that as well. Thanks!

johndi · 12th February 2011, 09:31 PM

How do you tell the difference from an older version 400a and a newer version?

Thanks
John

Redwingnine · 13th February 2011, 12:53 PM

The eariler units have a solid power cord coming out the back, while the later units have a IEC power cord setup. Many of the later ones also have a different label on the LED faceplates (the worrd cascode is included).

I'm sure Nelson could provide more insight.

Redwingnine · 20th May 2011, 08:46 PM

Well, it's taken a LOT longer to finish this, but almost there.

Ran into a slight problem: While working on the driver board, accidentally cracked a diode. The board I've got looks slightly different from the schematics listed here on the site.

The cracked diode has a part number of 1N75A, which appears to be a old germanium type. Was wondering if a 1N4148 would work in place of the original. If so, will replace all of the diodes.

6th November 2010, 08:11 PM	#13
Zen Mod diyAudio Member Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain	OK if Guru sez , then you must obey if I can recollect my memory - there was a thread started few years ago by one bitchy guy , and I just couldn't understand how and why boyz (including Papa ) gave him so much help and information for his T. repair I think that there you'll find some more info about best outputs but - if Guru already give you advice - listen to him when you don't have experience ( in exact matter) of your own - you must trust someone . __________________ my Papa is smarter than your Nelson ! tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; Mighty ZM's Bloggg;I'm dumb

6th November 2010, 08:33 PM	#15
Zen Mod diyAudio Member Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain	so - dilemma solved __________________ my Papa is smarter than your Nelson ! tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; Mighty ZM's Bloggg;I'm dumb

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6th November 2010, 07:58 PM	#12
Redwingnine diyAudio Member Join Date: Apr 2010	Well, the most recent email I received from the Threshold repair guru strongly suggested that the output devices be replaced. Given that advice, was lookig at replacing the old devices with the following: ON MJ21193/MJ21194 If I read other threads correctly on DIY, this should be a drop im for the 400A, and provide better max voltage/current performance. Anybody actually used these on a 400A? If so, how did it work out?

9th November 2010, 12:38 AM	#16
Redwingnine diyAudio Member Join Date: Apr 2010	I'm ordering a rebuild kit from Jon S. at Vintageamprepair (thanks, Jon!). Also found a guy who will re-anodyze the faceplate. Will post pics once done.

23rd November 2010, 03:24 AM	#17
wkjeffers diyAudio Member Join Date: Nov 2010	I would really like to know who you found for the re-anodyzing.....I just bought one that could use that as well. Thanks!

12th February 2011, 09:31 PM	#18
johndi diyAudio Member Join Date: Jul 2007	How do you tell the difference from an older version 400a and a newer version? Thanks John

13th February 2011, 12:53 PM	#19
Redwingnine diyAudio Member Join Date: Apr 2010	The eariler units have a solid power cord coming out the back, while the later units have a IEC power cord setup. Many of the later ones also have a different label on the LED faceplates (the worrd cascode is included). I'm sure Nelson could provide more insight.

20th May 2011, 08:46 PM	#20
Redwingnine diyAudio Member Join Date: Apr 2010	Well, it's taken a LOT longer to finish this, but almost there. Ran into a slight problem: While working on the driver board, accidentally cracked a diode. The board I've got looks slightly different from the schematics listed here on the site. The cracked diode has a part number of 1N75A, which appears to be a old germanium type. Was wondering if a 1N4148 would work in place of the original. If so, will replace all of the diodes.