I have a Quad 405 that I bought as 'spares or repair'. It took ages to get it stable but in the end it worked perfectly. If I remember correctly it was not easy finding correct output transistors.
Great! From memory there seems to be a consensus on one of the Quad 405 enthusiast sites for an OnSemi part which is a good substitute, which is what I ended up using.
@@audionautica6843 I took a quick look at my 405. The output transistors on one side had caption 2N3773. On the other side no caption was visible. Now, ten years after getting it working I am not sure on which side I installed new output transistors.
@@audionautica6843 I took a look with special lighting and close-up specs. Transistor markings right side of amp: ON, 2N3773, MEXICO, BM0231 Transistor markings left side of amp: RCA, 2N5038, HNS 8148
What would be your best guess on the component that started the failure? I'm guessing it was one of the 15V Zener diodes that got tired, but what do I know? It would be interesting to take them up to their max current for a bit and see how they act. Too bad you had to go back in, but at least your speaker protection add-on and the fuses did their job.
Yeh, who's to know. I read on a few forums about the Zener getting tired so that may well have been it. My hope is there isn't some other issue hiding behind the scenes that will pop up again requiring a third go.
Hi , great informative video, I'm just in the middle of recapping one of these using your videos as a guide, my question is the two Nicichon Muse caps you have fitted are bipolar where as the originals aren't, am I ok to fit two muse bipolar caps ? And what value are those two caps please? Thanks 👍
@@audionautica6843 Peter Walker conducted very careful tests with statistical analyis of the subjective opionions of listeners which showed that there was no detectable difference audibly between 405 and 303.
I've never worked on a 405 myself, but my understanding is that over time the 405 evolved into the 405-2. Ie, the later 405s had seperate protection boards which where then incorporated into the main PCB in the 405-2. The service manual shows the various difference. There are also some pretty good web sites out there about the 405 and 405-2. They also talk about various ways of "improving" 405s.
... a DC level on the output, if any, ought to be in mill volts ... another thing, you've fitted yet another pair of bulk capacitors even though you put a pair of new ones in the previous video ... why ?
Please read up before posting, as these faults are all classical. The R7/8 that caused this fault, must be replaced by at least 1W 3k3 or it will blow again. The classical faults are different related to PCB rev.
Bravo .. I hate British politics .But i love British engineering .. I love Quad amps and speakers ..And cars .... I will now go to a German site and tell them the same story .
Beauty is in the eye *ear* of the beholder. I haven't used mine a lot for HiFi, have noted it is a bit bass heavy IMHO. These do have a cult following. There are some in the know much more than I who would not agree that these don't sound good. See here: liquidaudio.com.au/quad-405-power-amplifier-review/
A nice investigation and repair..
Thanks!
Just bought one of these… Love it!
Awesome!
I always replace the Zener's with 1.3 Watt ones as recommended by Quad!
I have a Quad 405 that I bought as 'spares or repair'. It took ages to get it stable but in the end it worked perfectly. If I remember correctly it was not easy finding correct output transistors.
Great! From memory there seems to be a consensus on one of the Quad 405 enthusiast sites for an OnSemi part which is a good substitute, which is what I ended up using.
@@audionautica6843 I took a quick look at my 405. The output transistors on one side had caption 2N3773. On the other side no caption was visible. Now, ten years after getting it working I am not sure on which side I installed new output transistors.
@@v8pilot Date code?
@@audionautica6843 I took a look with special lighting and close-up specs.
Transistor markings right side of amp: ON, 2N3773, MEXICO, BM0231
Transistor markings left side of amp: RCA, 2N5038, HNS 8148
@@audionautica6843 YT keeps deleting my replies...
What would be your best guess on the component that started the failure? I'm guessing it was one of the 15V Zener diodes that got tired, but what do I know? It would be interesting to take them up to their max current for a bit and see how they act. Too bad you had to go back in, but at least your speaker protection add-on and the fuses did their job.
Yeh, who's to know. I read on a few forums about the Zener getting tired so that may well have been it. My hope is there isn't some other issue hiding behind the scenes that will pop up again requiring a third go.
Thank you, really helpful video, well done 👍🏻
Thanks for watching!
Nice done 👍
Nice Job!
Thanks for watching @tweakerman.
Hi , great informative video, I'm just in the middle of recapping one of these using your videos as a guide, my question is the two Nicichon Muse caps you have fitted are bipolar where as the originals aren't, am I ok to fit two muse bipolar caps ? And what value are those two caps please?
Thanks 👍
Yes, they are fine. I have made the Bill of Materials available for my Patreons. If I recall the value is the same as the originals.
@@audionautica6843 Thanks for your help 👍
very good
Hello, can you tell us what the function generator program for your iPad is? Thx!
I found it on the App Store, just find one that looks like it will work for you - I think it was free.
What's your opinion of the 405-2 ? Is it better than the 303 ?
Sorry - I've never heard a 303.
@@audionautica6843 Peter Walker conducted very careful tests with statistical analyis of the subjective opionions of listeners which showed that there was no detectable difference audibly between 405 and 303.
Can my Quad 405 be upgraded to a 405-2?
I've never worked on a 405 myself, but my understanding is that over time the 405 evolved into the 405-2. Ie, the later 405s had seperate protection boards which where then incorporated into the main PCB in the 405-2. The service manual shows the various difference. There are also some pretty good web sites out there about the 405 and 405-2. They also talk about various ways of "improving" 405s.
... a DC level on the output, if any, ought to be in mill volts ... another thing, you've fitted yet another pair of bulk capacitors even though you put a pair of new ones in the previous video ... why ?
Two different amplifiers mate. I left the originals in this one as they tested fine.
nice.
Please read up before posting, as these faults are all classical. The R7/8 that caused this fault, must be replaced by at least 1W 3k3 or it will blow again. The classical faults are different related to PCB rev.
I did and I have, but I will check it again...
Bravo .. I hate British politics .But i love British engineering .. I love Quad amps and speakers ..And cars .... I will now go to a German site and tell them the same story .
🤣
carbon resistor
Wgat the hell. This amplifier has glass epoxy boards.
Good work, but even fully rebuilt, they sound awful compared to good amplifiers.
Beauty is in the eye *ear* of the beholder. I haven't used mine a lot for HiFi, have noted it is a bit bass heavy IMHO. These do have a cult following. There are some in the know much more than I who would not agree that these don't sound good. See here: liquidaudio.com.au/quad-405-power-amplifier-review/
The great thing about the QUAD 405-2: They don’t ‘sound’, they just amplify.
@@sleiborg Then you know, or have learned nothing 🤣🤣🤣🤣🤣
@@sleiborg Absolutely. If you can hear a 'sound' of a Quad amp. you have a defective amplifier.