Quad 44 MK II relay jerking.

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01-Sep-2019 10:40 AM

French Quad

French Quad

Posts: 4

Hello Joost and Stefaan,

I am the owner of the Quad 44 preamplifier No.14569, therefore the second generation of this device (so called MK2). This information may be quite relevant for the following.

I recapped this preamp with the Dada Quad 44 MKII DIY Upgrade and Revision kit Deluxe. Some sensitive components being too old, they have been replaced by new ones and the other necessary modifications that you recommended have allowed a very clear sound improvement for this preamp. This is a very good idea from you, I thank you for that.

However, a problem has persisted well before recapping. After one to two hours in operation (warming-up?), the protection relay located on the right side of the M 12436-5 motherboard vibrates in a jerky manner at the beginning of the event, then continuously. This results in a very strong sound degradation (distortion like) heard in cabinets connected to my 405 amplifier output. The phenomenon stops immediately by switching off the 44 mains and then putting it back into operation. Then, this problem occurs again after 15 to 20 minutes after restart.

A quite similar problem had already been reported in the past on your blog (Blogspot, Friday January, 8th 2010), but this advisable relay voltage apparently did not match with the version of my 44 (MK2).

The original relay was therefore replaced by a new one (same operating voltage, same pins arrangement as the original one),but the phenomenon remains exactly the same.

The problem would not be at the relay itself (even if it's a good thing to replace it): I presume a malfunction somewhere into its control circuit.

Could you please help me to solve this problem that does not allow me to properly enjoy the quality of my 44?

With many thanks in advance.

Best regards,

Martial (France)

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01-Sep-2019 01:30 PM

EJP

EJP

Posts: 1644

We've written a lot in the blog about this over the years, with low Vf diodes and new relays and all the rest of it, but my most recent conclusion is that it is actually the W02 bridge rectifier losing output voltage with heat, which causes the relay to chatter without affecting anything else. Replace it with a W04 and see what happens.
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02-Sep-2019 04:21 PM

French Quad

French Quad

Posts: 4

Hello,

Thank you for your quick response. I will put your recommendations into action.

Best regards,

Martial (France)

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