Author Topic: My trusty Quad 405 MK 1 is fixed!  (Read 843 times)

Offline skollie

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My trusty Quad 405 MK 1 is fixed!
« on: December 18, 2017, 10:36:25 PM »
A really difficult and 3-month long convoluted journey.

It was only a dead l/h channel. With the assistance of a friend's recommendations and some suggestions from DADA Electronics, I replaced many components - bipolars and some resistors but it kept blowing 1 4A fuse on the L/H board. I can solder carefully and neatly but admit I really am a dufus  and didn't really know what I was doing.

It was then that I gave the faulty board to my friend who is also not an audio electronics person, being a retired Telkom test equipment tech.

Anyway, last night he called me and informed me there was 1 faulty new bipolar ex Communica and this, together with 1 open circuit resistor which was replaced and the fused stopped blowing.

So this morning, we set it up with a pre-amp and both channels worked after many weeks of frustration but...

The faulty board's heatsinks were very hot :'(

After the tecxh left, I had another close look and found one of those black transistors +- 1mm away from its heatsink as its screw had a stripped thread...

After hunting through my bins of idential boltsand nuts, I fastened the blerrie thing properly to its heatsink and all is cool and played like it used to - no more overheating.

All I'm looking for now is a worthy replacement for my stolen Sansui 317 MK11.

skollie

 
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Offline charles

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Re: My trusty Quad 405 MK 1 is fixed!
« Reply #1 on: December 19, 2017, 08:05:54 AM »
Andre, I am glad to hear that your Quad 405 MK I is now fixed.

Offline skollie

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Re: My trusty Quad 405 MK 1 is fixed!
« Reply #2 on: December 19, 2017, 10:33:51 AM »
Thank you Charles ;D It's hell and frustrating to know I may be a distant relative of Dumb and Dumber.

Regards

andre

 
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Offline skollie

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Re: My trusty Quad 405 MK 1 is fixed!
« Reply #3 on: December 19, 2017, 10:03:37 PM »
Alas. A false alarm. The 405 is still overheating - so much one can't touch the lefthand channel's heatsink after 30 minutes, yet it plays on both channels and no blown fuses :'( Running so hot the heat has spread from the l/h channel heatsink to the entire front fluted heatsink/casing.

Before this happened 3 months + ago, it was totally reliable and ran cool. Schitt!!

skollie
If you don't like my principles, I have others - Groucho Marx

Offline christowp

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Re: My trusty Quad 405 MK 1 is fixed!
« Reply #4 on: December 20, 2017, 03:38:25 PM »
Did you try Albertronics? Give him a call

Chris


Offline seanjammy

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Re: My trusty Quad 405 MK 1 is fixed!
« Reply #5 on: December 20, 2017, 10:45:51 PM »
Nilam repaired a 306 for me and seems to know these things backwards. Give him a shout?

Sent from my SM-G950F using Tapatalk


Offline skollie

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Re: My trusty Quad 405 MK 1 is fixed!
« Reply #6 on: December 21, 2017, 02:17:16 AM »
Thanks for the kind interest, guys. The gentleman who has been assisting me has been a good friend of mine for many years. I kept the amplifier throughout all of these frustrating weeks and he (my friend) only has posession of the faulty left channel's board and heatsink.

The amp is now in its entirety with me and tomorrow, I will again look at the faulty board with a strong light and magnification. BTW, all new transistors have been fitted with white paste and each item has new insulation strips.

It was just by pure chance that I spotted the transistor which was 1mm away from the heartsink which I thought had cured the problem as for the first time in several months, both channels worked properly for about 5 minutes before things got hot again but no fuses blew

Todays's testing was scary. As mentioned lots of heat spreaded also to the fluted heatsinks across the front panel but no blown fuses..

After tomorrow's close inspection by myself and if I can't see anything obviously wrong, I will leave it until after the season days are over.

My friend this evening mentioned oscillation outside the audio band which we will check for with my oscilloscope shortly.

I noted your recommendation re Albertronics and will consider after giving my friend another chance.

skollie


 
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Offline skollie

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Re: My trusty Quad 405 MK 1 is fixed!
« Reply #7 on: December 22, 2017, 05:38:18 PM »
I wrote too soon re this boring topic about an amp many people despise for whatever reason. Anyway, I like it and as written above, the dead left channel works again and doesn't blow one of the 2 aA fuses on the board.

During 5 to 10 mins playtime, the board's heatsink overheats a lot. After halfhour playtime, something on the left channel board overheats the entire heatsink including the fluted front casework - so hot that one can fry eggs on it.

I'm giving the friend who has been helping me needs a Christmas break so I want toi have a look see if I can discover why the channel is overheating so much.

The amp is currently connected a a pr of Denon 8ohm speakers  a pre-amp and a radio for a source. And Unplugged from the mains and most of the covers off.

All 4 transistors have been replaced with Dada's best recommendations and the loose transistor's heatsink has been properply fixed with its insulating strip and white paste.

My question: Will it be safe to use a pair of surgical gloves to try and probe WHERE on the bloody board the heating originates from with everything connected and the mains switched on? There are many sharp objects on the board and I will take care not to puncture the glove.

skollie

If you don't like my principles, I have others - Groucho Marx

Offline fdlsys

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Re: My trusty Quad 405 MK 1 is fixed!
« Reply #8 on: December 22, 2017, 06:25:47 PM »
Cell phone camera sees IR. Photo application must allow you some form of manual exposure or at least a "night shot" mode. Obviously, amp should be in the dark.

Off the top of my head, the only components that are able to radiate that much heat that you describe without self destroying are transformers, rectifier bridge and output transistors.

Has your friend biased it correctly; after the amp reached the normal operating temp?
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Offline skollie

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Re: My trusty Quad 405 MK 1 is fixed!
« Reply #9 on: December 22, 2017, 10:14:24 PM »
Thanks for the tips, Fdlsys

I am so stupid with such things. I have heard the term "biasing" but have no clue as to what is involved. I'm sure my friend knows what is involved and I will pass on your message after the holidays. Mobile phones are not my favourite pic takers. The one I have now is Android (dunno what this means) and one cannot donwload its pics, I do have a Nokia E95 which takes very good pics which I can download to my computer. I'll try using the Nokia.

Merry Christmas to you and your family and best wishes for 2018

skollie
If you don't like my principles, I have others - Groucho Marx

Offline Katji

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Re: My trusty Quad 405 MK 1 is fixed!
« Reply #10 on: December 22, 2017, 11:49:49 PM »
Android is the mobile Operating System, built by Google.  (Like Windows Mobile, iOS (or whatever Apple calls theirs, and the various other proprietary ones.)  Free, implemented somewhat differently by different device manufacturers. Why you get a decent OS on even cheap smartphones.

You want to upload pics to computer...it can definitely be done. Is it a Samsung? - That would make it easy, to tell you.  But anyway, there is probably an Apps button...tap it and look for one named something like File Explorer.

Samsung...the File Explorer has a button to show image files, I have it ordered by date-time, so the photos I just took are at the top of the list. Hold finger on one until it allows you to select the files you want - it shows a check mark (or tick) = and then the menu option Send...choose Bluetooth, it says Bluetooth is switched off, Do you want to switch it on - Yes ... and it shows a list of available Bluetooth devices, I tap "My ASUS" (my laptop) and it starts sending them. To the Windows folder Documents\Bluetooth Folder.

Offline skollie

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Re: My trusty Quad 405 MK 1 is fixed!
« Reply #11 on: December 23, 2017, 12:46:56 AM »
Hi Katji

The mobile pestilence started when spent 6 weeks in hospital in January and February this year.

My brother bought me a gift of a phone with all the bells and whisles of up to date phones. The icons and operating ways were radically different to my old E95 which I still have.

I doin't really like people to 'give' me things so I gave my brother's phone back and bought a similar up to date thing.

In the past, I only used the old Nokia to occasionally call my late wife or speak to Chubb. Really backwards I am.

The thing I have now, takes nice pics but each time I try downloading them to my computer, it doesn't download - instead it sucks up hundreds of pics on my  computer gallery :headbanger:

The call someone, the digits are perfectly in size to use without problems. When sending a whatsapp or sms, the digits are so small they are practically useless.

Last of the many hateful features - its outdoor/vibrate loudest is so socft, I never hear incoming calls. I don't want rash music rings - it must ring like a landline phone which  got it set on. Worst of all, it continually reverts to soft ring, no vibrate. The brand? K@kphone.
skollie
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Offline fredeb

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Re: My trusty Quad 405 MK 1 is fixed!
« Reply #12 on: December 23, 2017, 06:41:03 AM »
From a quick look at the service manual it appears that there are no internal adjustments ( bias or offset ) to be made to these amplifiers .

The Android phones can be quite handy once you get the hang of them Skollie . For example , what Fdlsys is referring to , is downloading an application from the Google Play store , in this case an application that turns your camera into an infrared camera . Problems like small text , can be changed in the settings ( either Whatsapp settings or phone settings ) . It will be good to sit with someone who know how to operate the phone for an afternoon - so they can show you the ropes .

I can highly recommend an android phone with a really large screen . Sometimes a cover also helps one to not accidentally push the buttons on the side of the phone - thereby turning the ringtone volume down or off . I hope this helps a bit .
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Offline skollie

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Re: My trusty Quad 405 MK 1 is fixed!
« Reply #13 on: December 23, 2017, 11:24:36 AM »
Thanks, FredeB

I know a couple of wiseguys whom I meet every Wednesday night. I'll ask them how I can do this.

Cheers & a merry Christmas and best 2018 ever.

In the meantime, I'
ll try the surgical gloves thing.

I bid thee all a fond farewell... ;D

skollie
If you don't like my principles, I have others - Groucho Marx

Offline fredeb

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Re: My trusty Quad 405 MK 1 is fixed!
« Reply #14 on: December 23, 2017, 05:28:47 PM »
Thanks, FredeB

I know a couple of wiseguys whom I meet every Wednesday night. I'll ask them how I can do this.

Cheers & a merry Christmas and best 2018 ever.

In the meantime, I'
ll try the surgical gloves thing.

I bid thee all a fond farewell... ;D

skollie

Happy Merriness to you too Skollie ! Don't kill yourself by feeling around that amp with latex gloves , rather get the other Leak fixed .  ;D
...evolution is the gradual development and stratification of progressive series of wholes, stretching from the inorganic beginnings to the highest level of spiritual creation.
Jan Smuts