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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Pre amp output shorted?
Pre amp output shorted?
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Old 20th March 2012, 11:41 AM   #31
epicyclic is offline epicyclic  United Kingdom
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Join Date: Jan 2012
Realising im asking questions so will just type

When connecting the scope probe to an earth connected piece of equipment you may or may not need to attach the crocodile clip to chassis ( not need to if scope is earth connected ). If you take the sprung hook end off the probe be aware that the metal band near the point is the earth side of the scope ( the same point as the crocodile clip ).

Happy hunting .
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Old 20th March 2012, 01:41 PM   #32
epicyclic is offline epicyclic  United Kingdom
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I have just had a thought........based on the fact that inserting the headphone jack causes the amp output to be muted ( the relay has and has not operated ) and also the fault on the left channel ( has worked has not worked ) .....is there a piece of loose metal floating about inside the headphone socket or are there some failed solder joints at the headphone socket .
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Old 20th March 2012, 09:33 PM   #33
SimpleMind is offline SimpleMind  Germany
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Quote:
Originally Posted by epicyclic View Post
I have just had a thought........based on the fact that inserting the headphone jack causes the amp output to be muted ( the relay has and has not operated ) and also the fault on the left channel ( has worked has not worked ) .....is there a piece of loose metal floating about inside the headphone socket or are there some failed solder joints at the headphone socket .
Good evening epicyclic,

that's an idea, which also dawned on me. I have to desolder and remove the jack to see, whether there is something broken or some metal inside. It is a possibility as I have already found one or two old solder pearls from a past repair (which the seller did not mention).

I have another good news: Canton sent me the circuit diagram for the preamp via email. I have asked now, whether I am allowed to share the diagram here. I don't want to violate their copyright after they have been that helpful, so I wait for their answer. Nevertheless I could send you the diagram directly via email, if you are interested. It sure is an interesting layout.

Ben
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Old 20th March 2012, 10:08 PM   #34
epicyclic is offline epicyclic  United Kingdom
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Hi Mind

Yeah very interested to see schematic . Could you send it via the private message facility on here .
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Old 21st March 2012, 12:51 PM   #35
SimpleMind is offline SimpleMind  Germany
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Quote:
Originally Posted by epicyclic View Post
Hi Mind

Yeah very interested to see schematic . Could you send it via the private message facility on here .
Hello epicyclic

I even got Canton's permission to upload the schematics here, with some quite understandeable caveats:

Canton Elektronik GmbH + Co. KG (see Lautsprecher | CANTON - German loudspeaker tradition - Deutsche Lautsprecher Tradition seit 1972 (de)) retains the Copyright for the circuit diagrams and has not given the diagrams into the Public Domain. So my message to all here, interested in the diagram: handle it respectfully and watch the Copyright.

I must say, I am very positively surprised by the service Canton provides to a customer, who uses a 20 years old product - that's very nice.

Some explanantions:
- the schematics have some short notes in German. and I'll give a summary here in English:
. generally they show only one channel. On the board all components with a leading "1" desginate the left channel (R1xx, C1xx, IC1xx etc.) whereas all components with a leading "2" designate the right channel.

- in the schematics the simple word "out" sumarizes three output connector sets (2 x RCA and 1 X symetric XLR)
- the part HIFI4:CTNPLAN1 is the phono section
- the part HIFI4:CTNPLAN2 is line section and power supply
- here "Kopfhöreranschluß" = headphone connector

So, that will give us a much better idea about the inner workings of the preamp.

Ben
Attached Files
File Type: pdf Canton EC-P1 preamp parts list.pdf (81.5 KB, 73 views)
File Type: pdf Canton EC-P1 preamp diagrams.pdf (181.8 KB, 89 views)
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Old 21st March 2012, 12:59 PM   #36
epicyclic is offline epicyclic  United Kingdom
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Hi Mind

Yes a big thankyou to Canton....
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Old 23rd March 2012, 10:16 PM   #37
dmfraser is offline dmfraser  United States
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Before you pull the relays make sure the relays are actually getting power. It is more likely the coil drive circuit has failed as you never get 2 relays failing at the same time in the same way. It is far more likely that the drive circuit is not activating the coils

As for4the voltage regulators, look up the pinout on the internet. What would be the base lead if they were a transistor is the input lead and the readings you have on the +7818 are normal. The 7818 is I-G-O and the 7918 is G-I-O. G= ground, I= input and O = output.

It sounds like you ar einover your head here and if you want to keep this item, you need to have someone local who is more of an expert look at it.

DO NOT change the relays until you are sure they are getting a drive signal first.
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Dan Fraser
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Old 24th March 2012, 10:33 PM   #38
SimpleMind is offline SimpleMind  Germany
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Join Date: Mar 2009
Quote:
Originally Posted by dmfraser View Post
Before you pull the relays make sure the relays are actually getting power. It is more likely the coil drive circuit has failed as you never get 2 relays failing at the same time in the same way. It is far more likely that the drive circuit is not activating the coils

As for4the voltage regulators, look up the pinout on the internet. What would be the base lead if they were a transistor is the input lead and the readings you have on the +7818 are normal. The 7818 is I-G-O and the 7918 is G-I-O. G= ground, I= input and O = output.

It sounds like you ar einover your head here and if you want to keep this item, you need to have someone local who is more of an expert look at it.

DO NOT change the relays until you are sure they are getting a drive signal first.
Hi Dan

Thank you for your very wise and considerate opinion and warnings. But epicyclic got me on something with his remark, that he would look more closely on the headphone stage.

First I replaced the relay, complete with its driver transistor and ofcourse (as mentioned above) replaced my wrongly chosen zener diode with the correct type. The relay than switched correctly as it should, but the left channel was still dead.

So I got my 2-channel analogue oscilloscope and simply tranced the signal on both channels in parallel. The circuit diagram I received from Canton was obviously the one missing part, I needed. So I found, that the left channel was lost on the main pcb, just at the soldering points, where a lead goes to the volume and balance control pcb. That was it: two of the five leads had broken away from their solder points, but you couldn't see it, as they have very thick insulation, which somehow still was glued down to the pcb and was thus hiding the broken leads.

I resoldered the two leads and now everything is fine and back in working order!

Thanks so much for all of your help and encouragement. Next is my old Denon DRM-800 Tape, where one channel is way too muted, than another old Pioneer CTF-1000, which needs new belts and a replacement switch, than the dead display of and older HK receiver. And than I want to start building new speakers. So, lots of fun over the spring and summer to come.

Ben
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Old 24th March 2012, 10:43 PM   #39
epicyclic is offline epicyclic  United Kingdom
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Hi Mind

Glad you have got it working .
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