Quad 44 input problem

[Icarus]

Hello All
I am a new member & this is my first post.

I have Quad 44 serial number 32387, which is I believe a late one.
I had the 44 & my 405-2 serviced by Quad. The following problem began after the service.
I have a problem with the CD/AUX input. Any source plugged into it sounds a lot quieter & is a much 'smaller' sound. Allmost a 'tinny' sound. If I swap the input card with the Radio card then the CD/AUX input sounds normal & the problem is on the Radio input. This would suggest the problem is not the input card but on the main board.
I sent it back to Quad, but the engineer could not hear any problem. He could not understand why his work, just replacing caps would cause this problem. Quad have washed their hands of it.
Can anyone suggest what might be causing this.

Thanks
Icarus

[burbeck]

hi Icarus
i am fairly familar with this unit, from what you describe the problem does lie on the mainboard, i would suspect one of the cd4066 switch ICs as faulty, the IC400 is the chip that switches aux and cd inputs. these parts are less than a quid to buy. hope that helps.

there is an issue with these parts they are very prone to static charge more so than normal run of the mill chips, so if you are going to tackle the job yourself drop me an email for tips

[Icarus]

Hi Bob

Thanks for your suggestions, good to hear your diagnosis as it confirms what someone else has suggested.

Unfortunately I can not send emails, mew member.

I will do the work myself, or ask a friend to do it for me.
Correct me if I'm wrong, are there not 4 of these 4066 ics ?? Do I need to change all of them ?
What would you suggest I replace them with, any particular 4066 chip ?

Thanks for your help.

Icarus

[jaycee]

It's probably worth replacing all of them. Newer devices will have much improved spec which should lower distortion a bit. They're also pretty cheap.

They must be the CMOS type, not the "74" series type as they need to be able to handle being powered from 15V.

Out of all of the types, OnSemi's MC14066B seems to be the best, but I doubt there's much in it.

AS noted above these devices are easily damaged by static - this was never factored in with early designs using them, meaning that its possible to damage them just by touching input sockets or ends of cables. I've not seen the Quad amp in question but I will be willing to bet there's no clamp diodes on the input to protect the 4066's.

[burbeck]

hi

yes there are 4 of these in the Quad they are marked on the circuit board IC400, IC401, IC402 and IC403. the one for Cd and Aux is IC400.

some companies no longer stock the DIL version here is a good source
http://uk.farnell.com/texas-instrume...18v/dp/1106112

i agree replace all 4 of them any way, be very carefull with static, once they are in circuit no problem. double check they are replaced the correct way round.

[Icarus]

Thanks all for your help/advise. I will order 4 x 4066s from Farnell & report back.

Cheers Icarus

[burbeck]

hi how did you get on with quad?

[Icarus]

burbeck

No have not done this yet. I was sing a different input & now am not using it at all.

However I will post back when I do get it done.

Cheers Icarus

[Tyron]

Hi Icarus,

I wonder if you fixed the 44 and if so what was the problem? It would be very interesting to know please!

Regards,

Tyron