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Denon AVR-1912 E2/EA

Michael Studio1

Jan 5, 2018
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I shall replace ZD800 (see page 185-6-7 for AV_B'D parts) regardless.since it has inconsistent Ω readings when one leg is pulled and totally different when totally extracted. It is a <ZENER DIODE> Searching the Cct. Diag. is one thing - finding the components on the AV PCB is a totally different thing. Most of the components are SM. Try as I might I cannot find that IC800-A and B. on page 114. It is possible that it doesn't exist like the pair of IC27:A and B on the top of page 126 on the HDMI_B'D. The resistor R871 is not on the Parts List and is in a boxed in area designated 'OPTION_A' so maybe the +7v. rail does not extend to this area.? which means the voltage isn't affected.and that NPN Transistor isn't an issue. I have applied an in-Cct. test by dvm on C808 and C823 resulting in 'open' on both Caps. C823 shows 116.8μF and C808 shows the same - both having an ESR=0.52Ω. For Cap tests I use a PEAK atlas ESR70 - very small and potent for in-Cct tests. I have ordered a Zener - they're supplied in packs of 20 for £2.22 - free delivery from RS Components Ltd. UK. Until the new Zeners arrive (tomorrow) I can make no further progress. Any comments? Michael Studio1.UK 13:26GMT
 
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Michael Studio1

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New Zener Diodes have arrived (already!) Q: Which way round do they go? A+8V CN14 pin 14 direct to the Black end and IC801 pin 80 to the Orange end? - or is it the other way round??? Michael Studio1 UK 13:28GMT
 
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Tha fios agaibh

Aug 11, 2014
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Orange shold be anode and the black represents the kathode side. Your meter should verify this.

Btw, you never mentioned what its forward voltage was. You tested it in with your dvm in diode test mode didn't you?
 
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Michael Studio1

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Orange shold be anode and the black represents the kathode side. Your meter should verify this.

Btw, you never mentioned what its forward voltage was. You tested it in with your dvm in diode test mode didn't you?
So sorry! Tha fios agaibh, and thanks for your speedy reply! Much appreciated. I measured the Zener in diode test mode with (-) meter on Cathode and (+) on Anode. The UNI-T UT61E has both Ω and Diode (selection by press button) Vf. Reads: 0.7378V.
I am not knowledgeable in the polarity requirement of a Zener diode - hence the Q. In the Cct Diag. (page 114) the Anode - or [ - is on the 'drop' side and the Cathode is on the +8V. side - or CP14 pin 14/15. Michael Studio1 UK 15:11GMT
 

Michael Studio1

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I got that the wrong way round! Apologies! the [ is the Cathode and the black triangle (any symbols available?) is the Anode. In the Cct Diag. the Anode is on the +8V. rail and the Cathode is going to IC801 pin 80. Michael.Studio1 UK 15:36GMT
 
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Tha fios agaibh

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I can't pull up your print right now but the symbol is similar to a conventional switching diode except the black line for cathode looks like a z. The annode is the arrow part that I think of as a sideways "A" and the line part almost looks like a "K" (cathode).
The difference with zeners is that they are often put in backwards (reverse biased) for voltage regulation.
 

Michael Studio1

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I can't pull up your print right now but the symbol is similar to a conventional switching diode except the black line for cathode looks like a z. The annode is the arrow part that I think of as a sideways "A" and the line part almost looks like a "K" (cathode).
The difference with zeners is that they are often put in backwards (reverse biased) for voltage regulation.
Yes, Tha fios agaibh, thanks for that info - I do believe this Zener is being used that way. The Cct.Diag. doesn't show it as a Zener - that info comes from the Parts List. So this is put in backwards to limit the Voltage from A=8V. to +7V for the IC801 My difficulty is in assimilating the knowledge of the use of a Zener. The current flow. Presumably this Zener has to be installed with the greatest resistance in the direction from the A+8V. rail to the IC801 Using the dvm at Diode setting, with the (-) probe on the Cathode wire and the (+) probe on the Anode wire the dvm reads: +0.74V. With the leads reversed there is no reading. Therefore if wired in to maximum resistance (the Cathode to the A+8V. and the Anode to the IC801, this should be delivering a hopeful +7V. to IC801. Am I right in this? If so that's how I shall solder it in place . . . Wait to hear from you. Michael Studio1 UK 20:23GMT
 

Tha fios agaibh

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Just took a quick glance at the print and it shows D800 as a 1n4007 (i know you already know this but I'm not totally up to speed here with all your tinkering) which is not a zener. It appears to just drop. the voltage by Its forward voltage. which is what, .7v?
So, I would install a 1n4007, ignore the partslist calling it a zener, and expect to see 8v on the supply side (anode) and about 7.3v on the load side (cathode).

Regarding zeners, (which I don't think d800 is) It's not best to think in terms of ohms imo.
Its better to think in terms of voltage and current.
But as you know, a zener will conduct/ let current flow backwards depending on the voltage. I don't know the voltage your Dvm applies across its leads in Ω setting, but obviously that would be a factor.
 

Michael Studio1

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Just took a quick glance at the print and it shows D800 as a 1N4007 (I know you already know this but I'm not totally up to speed here with all your tinkering) which is not a zener. It appears to just drop. the voltage by Its forward voltage. which is what, .7v?
So, I would install a 1n4007, ignore the partslist calling it a zener, and expect to see 8v on the supply side (anode) and about 7.3v on the load side (cathode).

Regarding zeners, (which I don't think d800 is) It's not best to think in terms of ohms imo.
Its better to think in terms of voltage and current.
But as you know, a zener will conduct/ let current flow backwards depending on the voltage. I don't know the voltage your Dvm applies across its leads in Ω setting, but obviously that would be a factor.

Thanks for the reply, Tha fios agaibh, VERY INTERESTING INDEED! this is going to be a l o n g reply as it contains a fundamental ERROR I have made. I looked at the diode's symbol Cct.Diag. and thought A-Ha! not a Zener! - but a Diode 1N4007. Q: why do they say it IS a Zener in the Parts List I wonder? (answer: look more carefully at the Parts List!) Now I have my 20 (Qty) 5.1V Zener diodes, BZX79C5V1 500mW (only cost £2.22 GBP) I can compare the look of them to the original which I removed - and they look identical. Not a Black cylinder with a Grey band at one end, but a translucent, much smaller, component made of some glass-like substance. Just as well I got 20 as one has just fallen on the floor and I cannot find it! Back to the main issue: identifying this component. I noticed, of course, there's an identically symbolled diode in the Cct.Diag. for the A-7V. rail right next to our diode leading from CP14 pins 16&17. I am looking for this right now. In the mean-time, looking at the identification marks on the AUDIO_VIDEO_PCB (right underneath the Zener itself, so you may not see it without removing the Zener) it is shown as a Zener Diode - with the Z bar as you described. I think it must therefore BE a Zener - like in the Parts List. and not an IN4007 as shown on the Cct.Diag. Also, of course, the symbol on the AV_PCB shows the way round that Zener should be installed with the 'Z' Cathode . . . WAIT a moment! There's another D800 on the PCB. and this is a Diode proper. It is ranged along-side D801 at the end of the Tuner/Antenna can, and between two Electrolytic Caps. Nos.C808 & C811. What have I done? Back to the Parts List (page 185) There's only one ZD800. That's the one I removed - so I must re-install it (with a new one) according to the printed symbol on the PCB. I must look at the Cct.Dig. to see just what I have done here! Mea Culpa Maxima! Then I must check this new-found D800 - which is described on the Parts List as 'D,SWITCHING 1N4007'. So, according to the Data Sheet from:-
ON Semiconductor, the 1N4007 has the following characteristics:-
Peak Repetitive Reverse Voltage: 1000V..
Non-Repetitive Peak Reverse Voltage: 1200V.
RMS Reverse Voltage: 700V.
Average Rectified Forward Current: 1A.
Vf = Typ. 0.93V. Max. 1.1V
Vf(AV) Max. 0.8V.
Testing the D800:
Applying the DVM in Diode Mode across D800 (the real D800 this time!)
DVM (-) to Anode, (+) to Cathode = 0 reading
DVM (+) to Anode (-) to Cathode = 0.621V.
Michael Studio1 UK 11:53GMT
 
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73's de Edd

Aug 21, 2015
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Sir Michael . . .et al . . . .

OBSERVATION and CONFIRMATION . . . .

Your D800 diode IS being just a common 1N4007 diode that is used in a steering diode function and comes from the REG_CNT 2/4 G10 as A+8V and then imparts the ~0.7VDC voltage drop across itself and then has that power line feed being redesignated as the A+7V supply line.

So put that new Zener back into stock and you are fixed for life.

BUT the original D801 was bad if not having that ~0.7vdc confirmation, in one direction.

73's de Edd
.....
 

Tha fios agaibh

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It's good that you caught your mistake Michael. You need eyes like a hawk to catch every detail. You might be out £2, but now you can experiment on the bench with your new box of zeners. :)

Back to diodes D800 and D801 feeding your 7v supply, make sure to check the negative side (D801) also. Hopefully that voltage isn't being pulled down also.
 

Michael Studio1

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It's good that you caught your mistake Michael. You need eyes like a hawk to catch every detail. You might be out £2, but now you can experiment on the bench with your new box of zeners. :)

Back to diodes D800 and D801 feeding your 7v supply, make sure to check the negative side (D801) also. Hopefully that voltage isn't being pulled down also.

Thank you for coming in on this, 73's de Edd. This has been a very confusing issue. I am trying to identify your reference to: REG_CNT 2/4 G10 . Is this page 111 in the Service Manual? What is G10? then I can study it. As to D800 and D801 I have just taken DVM readings (DVM set at Ω+diode button), where D800 = 0.62V.
and D801 = 0.63V. In both these tests the (+)probe was on the Anode and the (-) probe on the Cathode (or'K'). As for the Zener Diode (ZD800), I shall have to replace it since the original fell on the floor and is lost. The symbol etched on the PCB will give me the correct orientation. Michael Studio1 UK 13:30GMT (lunch time!)
 

Michael Studio1

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I wonder if G10 refers to a 'Northing' and 'Easting' on REG_CNT 2/4 - page 111 (as used in Ordnance Survey maps?) If so, then I am referred to CN14 connector in the SIDE CONNECTOR. Yes?
 
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Michael Studio1

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It's good that you caught your mistake Michael. You need eyes like a hawk to catch every detail. You might be out £2, but now you can experiment on the bench with your new box of zeners. :)

Back to diodes D800 and D801 feeding your 7v supply, make sure to check the negative side (D801) also. Hopefully that voltage isn't being pulled down also.

Thank you for this, Tha fios agaibh. I have found where this Zener is - it's on AV 1/3 (page 114) at K8. Now 73's de Edd has opened my eyes to this referencing!! These Zener Diodes are so very small I have lost the original and one new one . . . . somewhere on the floor of either the Studio or the Lab. However I have ordered some 1N7004's - but they come in packets of 50 so I have a real lot to experiment with on the bench - with an increasing price tag now + £6.86 (inc VAT) + those Zener diodes. I am about to solder in a new Zener. The symbol etched on the PCB shows the correct orientation. This symbol cannot be seen without removing the Zener - for it's underneath it. Michael Studio1 UK 14:35GMT
 

Tha fios agaibh

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I wonder if G10 refers to a 'Northing' and 'Easting' on REG_CNT 2/4 - page 111 (as used in Ordnance Survey maps?) If so, then I am referred to CN14 connector in the SIDE CONNECTOR. Yes?
Yes, exactly like a map reference. In this case, G10 points to cn14 at bottom of page 111. It'd be nice if they'd just give you the page # 'eh?

Sorry, I meant to check + and - power supply rail once you get Humpty Dumpty back together and powered up.
 
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Michael Studio1

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Yes, exactly like a map reference. In this case, G10 points to cn14 at bottom of page 111. It'd be nice if they'd just give you the page # 'eh?

Sorry, I meant to check + and - power supply rail once you get Humpty Dumpty back together and powered up.
Well, Humpty Dumpty is back together again - only the PCB structure though. As yet I haven't replaced D800 or D801. but I have measured their Vf with the dvm in Ω and applied the Diode button with the following results:-
D800 shows 0.62V. and D801 shows 0.63V. Will anyone comment on these readings? Michael Studio1 UK
17:08GMT
 

Michael Studio1

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AVR-1912 E2/EA powered up for Voltage (or should this be Revoltage) readings at Supply rails and IC801.
A+8V. rail (page 111 G10) +8.154V (CN14 pin14) reference to AGND
A-8V. rail (page 111 D10) (CP13A pin6) (-)7.82V. reference to AGND
Now to IC801 (page 114G5) IC801 pin 80 (AVCC) +3.36V reference AGND.
(page 114E5) IC801 pin 52 (AVEE) pin 52 -7.05V.
Michael Studio1 UK 18:08GMT (Tea time!)
 
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Michael Studio1

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Perfect Vf readings for most silicon diodes.
I trust they had almost infinite readings (open) when reverse biased?

Yes the readings in reverse were unreadable, Tha fios agaibh. The dvm said: '.OL' Off Limits? anyway, unreadable - yet read on my results from A+8V, A-8V, and the relevant Voltages at IC801 - just posted.
The Voltage reaching the IC801 at AVCC pin 80 doesn't make sense (still) Michael Studio1 UK 18:15GMT
 

Tha fios agaibh

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Michael, If I remember correctly, your problem was the 7v supply to ic801 was only 3.5v.

Either something downstream of D800 is overloading the supply, or the ps is unable to deliver the required current.
There are several approaches to finding the culprit, I like to use an isolation method to finding things but discretion should be used that it won't cause component damage.

You could use an external supply to inject the 7v into just that section to see if that gets pulled down also. Which would prove the ps side is ok.

Many ways to skin a cat.

I'm signing off now to have a cold one.

Regards, John
 
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