Denon AVR-1912 E2/EA loss of Left Audio  - Page 1
Forum section: electronics / repair

author: Studio1@29
author_rank: Contributor
timestamp: December 07, 2017, 03:10:18 pm
content: Denon AVR-1912 E2/EA (this is what it says it is on the screen when using the 'Special Mode Setting Button' as shown on page 19 of the Denon Version 6 Service Manual)It is proving quite difficult to trace injected tones/signal into VAUX L&R on the Front Panel.Test Equipment I am using: two simple variable freq. Audio Generators - one for Left and one for Right. A small battery powered amplifier with a home-made probe incorporating a 100Mfd cap. This system works very well on Analog audio. UT61E Multimeter. Peak ESR70 capacitance & ESR meter.Unfortunately I cannot 'source' a 'Jig for Servicing' (8U-110084S) kit as shown on page 43/44 which means the pcb's cannot be powered outside the chassis - which makes tracing signals virtually impossible due to the cuboid interconnections of the pcb's. This is some protective feature of Denon's where the unit simply turns off if any pcb's are disconnected.PROBLEM: Only a tone injected in the VAUXR channel appears at the 'Front' Speaker Terminals at the rear. Tone injected in the VAUXL disappears at IC801 (a 100 pin SM R2A15218FP) mounted on the Audio Video pcb)Does anyone have any suggestions, please? There's a possibility I can inject a tone into an un-powered pcb and trace it? Any comments? Thanks. Michael UK.

author: mzacharias
author_rank: Frequent Contributor
timestamp: December 07, 2017, 05:25:17 pm
content: Do at least try a factory reset as per the owners manual; It's worth a try and it fixes more Denon's than you would think.

author: Studio1@29
author_rank: Contributor
timestamp: December 08, 2017, 10:10:17 am
content: Thanks, M Zacharius - oddly enough I hadn't considered this because when I first got this AVR both channels worked but only the Right channel was OK, the Left channel was intermittent and depended on the pcb structure being 'twisted' to do so. So the previous owner had stuck in a length of 1/2" x 3/4" wood to hold the pcb structure in a 'twisted' working mode. I thought those pcb edge connector blocks must have a dodgy contact somewhere so, using my new HK branded 858D hot air soldering station I carefully reflowed all the solder connections on the edge connectors which create this four-pcb structure - but this hasn't worked and worse - I cannot 'twist' the pcb structure to get the Left channel to work now. This is why I thought it must be a component failure. Excuse the verbiage! Just thought you'd appreciate the run of events here! Now I shall follow your advice, download the 'User Manual' and try the Reset method you suggest. Thanks. Michael UK

author: Studio1@29
author_rank: Contributor
timestamp: December 08, 2017, 03:45:57 pm
content: Hello MZacharius. We have carried out a Reset as you kindly suggested, as per owners manual but there is no change. The Tone from the AFGenerators still only comes out of the Right Front speaker. My preparation has involved soldering on to two contacts on the Audio Video pcb at the last point where both tones can be heard - simply because without that 'Jig for Servicing' (as shown on page 43 of the Service Manual) these pcb's cannot be dismantled and still work. I have traced the VAUXL&R signal paths up to contacts 83 (VAUXR) and 84 (VAUXL) on the 100 contact IC801 (Service Manual p.168) on the Audio Video pcb. That is as far as I can trace with the AVR powered on. I did manage to dangerously pick up both tones with my probe and amp on two further contacts of IC801 and that was at pins: 53 (VAUXL) and 54 (VAUXR) so maybe I should move my injection of tones to that point with the AVpcb removed and see if they can be traced further without power. One further strange thing is that pin 83 is is i.d. as INL.12 and pin 84 is i.d. as INR.13 on the layout of this IC801 on page 168 of the Service Manual - i.e. the polarity is reversed. Michael UK.

author: oldway
author_rank: Super Contributor
timestamp: December 08, 2017, 06:13:57 pm
content: Is this your service manual ?https://nohm.eu/schematics/Denon/AVR-1911%20AVR-791%20Service%20Manual.pdfInput of VAUXR and VAUXL are pin's 56 and 57 of IC801, not pin's 83 and 84...Do you have an oscilloscope ? can you probe the pin's 56 and 57 of IC801 ?Have you a signal on both pin's ?Can you probe the pin's 2,8,10,14,16,20,22 ?Have you some signals ?You should understand that repairing such a highly sophisticaded gear need more modern way of repair than what was used with vintage amplifiers.I have worked in service of plasma and lcd tv's for LG and PANASONIC, whe where only replacing faulty boards, not trying to trace bad contacts, bad solders, interrupted printed board, nor faulty component.

author: mzacharias
author_rank: Frequent Contributor
timestamp: December 09, 2017, 11:33:02 am
content: Quote from: Studio1@29 on December 08, 2017, 10:10:17 amI wish you had included this important information in your original posting.It's beginning to look as if you would need to disassemble the unit and look for a circuit board crack, broken solder joint, etc on the underneath side of the main boards. Also check the associated speaker relay for proper operation. Despite the twisting routine prior, don't neglect the possibility of a bad solder connection at the main amp assembly - this was a fairly common issue with all the Denon's, Pioneer's, Marantz's, etc that used those 5 and 7 channel amp assemblies.

author: Studio1@29
author_rank: Contributor
timestamp: December 09, 2017, 12:17:29 pm
content: Thank you, MZacharius, for your interesting reply. I apologise for not including this info in my original post - I simply wasn't sure how much information to give, this being my first attempt at getting help on this EEV Forum. By 'Main Boards' do you mean the SPK_SMPS B'D's? I have not attempted to remove these as yet from the chassis. I think the Relay Units are on the SPK B'D. - four black rectaguloid components? Testing these boards out of the chassis does indeed show the need for one of Denon'e 'JIG FOR SERVICING' (Extension cable kit) shown on page 43 of the Denon AVR-1912 VERSION 6 Service Manual - but I haven't been able to source this. Denon's, I believe, only sell these to professional Service Engineers and I am certainly not one of those! I wonder if these kits are 'hireable'.I have been asked if I have an Oscilloscope. Yes, but only a pocket one! It is a simple 'DS201 pro' Pocket Size, Open Source (whatever that might mean) 200Khz bandwidth, 1Ms/s sample rate with 8M storage built in. Along with my pair of AF Signal generators, a PEAK DCA55 Transistor Tester and a PEAK ESR70 Cap. tester, a couple of E.V.M's this is my total kit. Plus the usual soldering irons and an 858D Hot Air Soldering Station. Most of m life has been in music - Piano and Harpsichord tuning and repairing for Glyndebourne Festival Opera for nearly 30 years. Now retired I have gone back to my early occupation of Location Recording using high end Mics (Calrec SoundField and ElectroVoice RE20's &c to Digital on Computer with Lynx TWO Multichannel Audio Interface. It was when the Digital daughter-board on this went wrong that I purchased the mini Oscilliscope to tell Lynx what was not happening . . . Michael UK.

author: Studio1@29
author_rank: Contributor
timestamp: December 09, 2017, 02:51:39 pm
content: Thank you, Oldway for taking the time and interest to help in this 'search for the Left tone'Although the Service Manual you have kindly given the 'Link' to is not exactly the same as the Version 6 I have, the Cct. Diagrams and their associated pages appear to be. I also note that the differences between the large pinout of IC801 on page 168 are the same as those differences in the Schematic Diag. on page 114. in my copy. Those differences (which affect my understanding of this IC801) are that pin 53 in the Schematic Diag (p.114) show it as 'NC' whereas that pin in the large print of IC801 on p.168 show it as INL12. But I do hear both L&R tones at pins 53&54. I also hear both tones at pins 83&84, but am in danger of shorting out pins using the probe on the miniscule pinout of IC801. Indeed, with a small spark this has happened - so I thought I had 'toasted' the whole AVR. However, on turning it on again I found it still worked! Phew! I must source that 8U-110084S (page 43, Service Manual) - (have I made myself clear in this description, I wonder? It looks somewhat convoluted)Test Equipment I have: Oscilloscope - small (7cm.screen) battery powered Open source (whatever that might mean), 200Khz bandwidth, 1Ms/s sample rate, 9M storage built in, PEAKE ESR70 cap. tester, PEAKE DCA55 Transistor tester, two E.V.Meters. That's it. Usual soldering irons & one of the 858D Hot Air Soldering Stations like Dave was dicussing on his eev/Blog a little while ago.My electronic knowledge is a bit limited, my use of equipment now I am retired being mostly in the Sound Recording world - high end Mics like Calrec SoundField, ElectroVoice RE20's,RE55's &c. and Schoeps BLM's &c into Lynx TWO-A Multichannel digital card.we have in our Studio.Most of my working life has been behind stage at Glyndebourne Festival Opera where for over 26 years until my retirement I was Piano and Harpsichord Tuner/Technician.Michael UK.

author: Studio1@29
author_rank: Contributor
timestamp: December 09, 2017, 05:46:26 pm
content: Yet one more strange variation from the printed Schematic Diagrams of HDMI UNIT (10/13) page 126. In my AVR-1912 E2/AE there is NO Dual IC27. It is physically non-existent. The SM soldering points are there on the HDMI B'D but these are (I suppose) by-passed and the signal goes straight through the Edge Connector CN2 in pins 4&6 > CP11 sockets 4&6 of FRONT_CNT B'D > the FRONT_CNT B'D to CP114 pins 17&18 > CN114 sockets 17&18 on AUDIO_VIDEO B'D (where I soldered my 'Tell Tails' and where both L&R Tones appear. Physical tracing by evm shows a direct connection for VAUXR through a 10mfd 50v electrolytic cap. to pin 83 of IC801 and pin 84 for VAUXL of IC801. My 'naughty' test probe gave Tones out of the IC801 at pin 53 ADCL and pin 54 ADCR before accidentally shorting two IC801 pins and causing the AVR to power down. (smack on wrist) However the AVR wasn't 'toasted' and powered up OK. This shows the need for the Denon Extension Unit Kit Set 8U-110084S which Denon will not sell to me as I am not a professional Service Engineer. (True) So unless I can hire a set for a duration or purchase one somewhere I am s t u c k.YET . . Maybe I am getting confused and the lack of IC27 has absolutely nothing to do with the loss of VAUXL tone. However, the VAUXL&R from the front panel appear at the HDMI B'D via that 40 x way ribbon cable from the FRONT_PCB. I find on page 130 of the Service Manual that the VAUXL&R channels go through Dual Op.Amp. IC102 on the V.AUX B'D (which could be why IC27 Op.Amp. is missing.) through pin 1&3 on CP103 and CN103.and arrive at Ccts. 6&8 of the 40 x way ribbon cable.That both L&R tones appear at the HDMI B'D proves that IC102 Dual Op.Amp is OK. Excuse my thinking-out-loud in this Post. Michael UK. 17:50GMT.

author: mzacharias
author_rank: Frequent Contributor
timestamp: December 09, 2017, 06:21:27 pm
content: Quote from: Studio1@29 on December 09, 2017, 12:17:29 pmI was referring to the "audio_video" board and the "SPK" board (speaker relay board) which includes tha main large filter capacitors. These boards are installed horizontally underneath practically everything else in the unit. I've spent many, many hours the past let's say twenty years since this type of construction became common, troubleshooting and trying to troubleshoot signal problems on units similar to this by Pioneer, Denon, Marantz, Yamaha, etc.You need to get a handle on what general area the problem exists. For example: Does the affected channel exit the 7-channel amp assembly OK? If so you have a relatively straight path from where it connects to the SPK board, to the relay, to the speaker terminal.It's helpful to have long pointy probes to really get down in there while it's running but sometimes you simply have to tear it apart and look for physical defects.

author: Studio1@29
author_rank: Contributor
timestamp: December 09, 2017, 11:34:57 pm
content: Hello MZacharius. Thank you for those suggestions which I will take action on tomorrow. Those pcb's are still in situ and revealed since the HDMI, the AUDIO_VIDEO B'D and the two CNT boards have been removed. It is now 23:35 hrs G.M.T.

author: Studio1@29
author_rank: Contributor
timestamp: December 12, 2017, 07:46:51 pm
content: Hello Oldway. There's been a minor hiccup here in the Workshop when I found the ceramic cap in my probe had broken and needed replacing - which I did successfully using a 2.2Mfd 50v, electrolytic (NEG towards the amplifier unit)I have resurrected an 'Endoscope' with 6 led's around the lens and probing with my Sound Probe. Great strain on the eyes, the endoscope, as the points of interest are so small as to defy numerical recognition. I can't quite see the fine point on my Probe to be sure which of the IC801 contacts it is touching. I have mounted the endoscope on one of those weighted alligator clipped, magnifying glassed bench third hand thingies. Otherwise it's akin to watching an amateur video where the cameraman has no notion of s l o w pan and the image dances around as a result. But this way I hope, when I have mastered the technique, to be able to probe the pins 1-30 and 31-50 which cannot normally be seen without dismantling the pcb structure.I am looking at your Post of 9th. December. You ask: "can you probe pins 2,8,10,14,16,18,22" I am hoping that with this 'Endoscope', and having mastered the technique, I shall be able to do these probes. What shall I be expecting at: SBR OUT(2), SLOUT(, SROUT(10), SWOUT(14), COUT(16), FLC(18), FROUT(22), (did you also mean to add FLOUT(20) as well?)I appreciate that this Denonj AVR-1912 is a sophisticated bit of kit - and I'm finding that out the hard way! However it didn't cost much in the first instance and it will be great to have been able - with your help and those of your eev colleagues - to be able to fix it! It is my 20yr. old son's - he's at Guildhall in London on a 3yr. Theatre Technical Course.I'll get back to you so soon as I am able to give an answer to your pinout questions.As to an Oscilloscope - what I have hardly warrants the name! It is an inexpensive Chinese hand-held 'DIY oscilloscope kit, which I found on e-Bay. DS201 pro. "Pocket size (7cm colour screen) Open source (whatever that might mean) 200Khz bandwidth, 1Ms/s sample rate, 8M storage, all in an Aluminium Alloy case (and a plush-lined black felt case with a security strap, probe with an alligator GND clip end, a spring-loaded cap (pull it back to reveal the probe end, or take it off entirely) a tiny DIY Allen key. (I can really do some damage with that!) and a mini CD to load the programme on the PC. Michael UK

author: Studio1@29
author_rank: Contributor
timestamp: December 12, 2017, 08:29:50 pm
content: Hello MZacharius - Further thanks for your interesting and helpful Post. There's been a minor 'hiccup' here in my Workshop. The ceramic cap in my home-made amplified probe broke. I wondered why I wasn't getting any tones out of the AVR and feared the worst - only to find the cause. Now with a new (but electrolytic) cap in the probe I can continue.To assist probing the IC801 contacts on the two sides which are out of sight I am using an endoscope with built in leds around the lens. This requires a lot of practice rather like using a mirror for the first time! The image appears on the Workshop monitor screen. It works but is difficult to be precise in placing the audio probe using the endoscope - everything moves so fast! - so I must master this before I can make any real comment on my progress.I want to follow the points you made about the 'affected channel exiting the 7-channel amp' - I'm not sure exactly where to find that exit point. Equally I'm not sure at which point and on which pcb, the Analog becomes Digital (and vice-versa).Probes. These I make out of thick piano wire (of which I have an enormous amount) I grind the end on my belt-sander to resemble a thin sewing needle.Michael UK

author: SoundTech-LG
author_rank: Frequent Contributor
timestamp: December 12, 2017, 10:21:11 pm
content: Have many, if not all the PCBAs for the AVR-1912 (USA 120V 60Hz version only) Also numerous working, and complete USA versions of the AVR-1912 available. If you ever figure out which board.

author: Studio1@29
author_rank: Contributor
timestamp: December 13, 2017, 09:42:39 am
content: Thanks indeed for your Post, SoundTech-LG. As a matter of interest, does the Mains Voltage (currently it is 244v., 60cps in my Workshop) matter on any pcb other than a Power pcb? It is Very Good Indeed to know there are spare boards available. First I am hoping to identify where the Left Tone stops, on which pcb and which component. I am not sure, as yet, if it is leaving the IC801 - though I DID get both at contacts 53 (as VAUXL) and 54 (as VAUXR) and these contacts are shown on page: 168 of the AVR-1912 Service Manual as: ADCL(53) and ADCR(54) which I interpret as both tones 'leaving here OK'. Next I need to establish where those two tones go from there. Since I can vary the pitch of either tone signal I can tell whether it is a Left or Right tone. Also the Right tone is getting all the way through to the Front Right speaker terminals. Please comment!Michael UK

author: mzacharias
author_rank: Frequent Contributor
timestamp: December 13, 2017, 06:46:49 pm
content: The HDMI board is usually different for different markets. Probably region coding and other permissions-related stuff.

author: Studio1@29
author_rank: Contributor
timestamp: December 13, 2017, 07:47:56 pm
content: Thanks, MZacharius. Yes, of course! I am only looking at this Unit as a piece of Sound kit - but, of course, it is more than that - I had forgotten. Michael UK

author: Studio1@29
author_rank: Contributor
timestamp: December 13, 2017, 08:10:44 pm
content: So far I have had no new results from my probings today. Everything is as it was with just the Right tone/signal appearing at FR speaker terminals. Now I am looking at the two aspects shown in the AVR-1912 Service Manual, that of the Block Diagrams (pages 29 - 42) and that of the Schematic Diagrams (pages 106 - 131) I find one very odd thing: all the Audio Block Diagrams show IC801 as being on the HDMI B'D - would that it were! It would be a doddle to probe then! As it is it's on the Audio Video B'D directly below it. Unless I am mis-reading the implications of the Block Diagrams! Anyone like to comment?I have now satisfied the question of how far the Left tone is going - at least I have traced it as far as the IC801 OUT at pin 53 (ADCL) VAUXL and pin 54 (ADCR) VAUXR. So it's leaving the IC801 OK. presumably on its way to be digitised. Now looking at the 7 Channel Amp. B'D, I note that each Channel has a dedicated 3-pin Test Point. What are these for? Anyone? Michael UK.

author: oldway
author_rank: Super Contributor
timestamp: December 13, 2017, 09:13:35 pm
content: I am doing amp and receiver repairs, mostly vintage 60's and 70's.Sometimes I also repair newer devices, but only stereo amplifiers and receivers, never 5.1 devices.M Zacharias certainly has a lot more knowledge than me about this kind of device, I leave him the placeNB: picture of my workbench....

author: Studio1@29
author_rank: Contributor
timestamp: December 14, 2017, 10:33:03 am
content: Thank you Oldway for your Post. I like the workbench photo - mine, I fear, is Very Cluttered Indeed and I have to rummage frequently! I'm having temporary problems with getting a picture from the Endoscope to show on the Workshop pc. When I have sorted that out I shall be able to probe those IC801 pins and hear what I hope for! When that happens I will Post the results. But it is still strange that the two images of IC801 on pages 168 and 114 (Schematic of Audio Video B'D) are different!. I am hoping M.Zacharius can throw some light on this - there again it may not have any importance! But both signal (L%R) are still there at pin 53 and 54 - and it is that pin 53 (according to the IC601 image on page 114) which is 'NC' - not connected? I must fire up the AVR and recheck this! CORRECTION!!! the Left signal is at pin 54 and the Right Signal is at pin 55. This was obviously a fault of mine caused by parallax - and not seeing too well (I'm having cataract problems in both eyes - so please forgive! The operation will be early 2018.)So I have established that the pinout of IC801 is as per that on page 114 - the Schematic Diagram of the Audio Video B'D. I'm Posting this and getting Breakfast. Michael UK.Time at 10:30 GMT

author: Studio1@29
author_rank: Contributor
timestamp: December 14, 2017, 10:43:38 am
content: NOTE!! IC801 PINOUT CORRECTION! Things are as per Schematic Diagram Page 114 Denon AVR1912. Pin 54 = AD_L (VAUXL) Pin 55 = AD_R (VAUXR). Michael UK

author: Studio1@29
author_rank: Contributor
timestamp: December 15, 2017, 05:51:11 pm
content: RESULT OF IC801 L&R TONE INJECTION AT VAUXL&R and what appears at IC801 pins:Injecting different frequencies. into VAUXL (low tone) and VAUXR (high tone) with an Audio Probe I have found the following (L) or (R) tones on the pins of IC801.Pins: 21 (L), 23 (R), 26 (L), 28 (L) 31 (R), 32(R), 33, (R), 34 (R), 44 (R), 45 (L), 46 (L), 47 (R), 54 (L), 55 (R), 83 (R), 84 (L).This test was very time consuming as an Endoscope was required to see this happening and viewed on the Workshop Computer,.The need to establish a good connection with those tiny contacts on the IC801 - many of them being out of physical sight and relying on parallax correction, (in this instance physical contact with a long bent and pointy probe was made more difficult by the contacts on the IC801 being at a different level to the SM contacts - hence the 'parallax' problem) recounts &c. (lose touch with the contact means starting all over again).So to the burning questions: are these results as expected?and:Where do I go from here to find that Left Tone?Over to you . . . . . Michael UK

author: Studio1@29
author_rank: Contributor
timestamp: December 16, 2017, 08:12:30 am
content: I am trying to follow page 114 of the Service Manual and need advice. I am following pin 54 (A/D_L) and 55 (A/D_R) of IC801 I am thinking (since I hear the relative signal tones at these points) that they are in the wiring 'loom' which arrives at CN114 pin 17 (VAUX_R) and pin 18 (VAUX_L) at the top of the page just below margin J&K. This is identified as REG_CNT 3/4 H8.Q.1: Could anyone please advise what this identification: REG_CNT 3/4 H8 means?Q.2: and where I will find it?Q.3: it looks as though it may be page 3 out of 4 of H8 (whatever H8 means)?? - there are several similar references at the top of page 114.Q.4: Am I right in thinking the signal tones are as yet still analog?Q.5: This may be a stupid question since on digitisation there will be no Left and Right. Is this correct?Q.6: I am looking for a CODEC component - is this on the Audio Video B'D?This is a steep learning curve for an Octogenarian! Many thanks. Michael UK

author: Studio1@29
author_rank: Contributor
timestamp: December 17, 2017, 02:39:13 pm
content: So I am following the VAUXL&R as they appear at OUT of IC801 as: A/D_L at pin 54 and as A/D_R at pin 55. To those of you used to reading these Schematic Diagrams, this will not be a surprise that these two Ccts. are shown individually within a broad 'arrow', showing direction of flow as <[A/D_L] and <[A/D_R] - the < pointing to the 'Loom' and ending at CN115 on the AUDIO VIDEO B'D at pin 17 (A/D_L) and pin 15 (A/D_R). This is where things get exciting! For the Right Tone appears at pin 15 (A/D_R) BUT the Left Tone does NOT appear at pin 17 (A/D_L) Somewhere between these two points then is the break in continuity. Michael UK. 14:38 GMT.

author: Studio1@29
author_rank: Contributor
timestamp: December 18, 2017, 02:08:36 pm
content: On the Audio Video B'D: page 114 Service ManualI have now proved conclusively that the Left signal gets through from IC801 pin 54, through SM R847 but does NOT arrive at CN115 pin 17.So there's an open Left Channel on the Audio Video B'D. Close inspection on the foil side shows two mini solder blobs - or Test Points - in that particular area of the signal path. Monitoring these blobs (physically positioned on the pcb at 33cms from the edge of the pcb (next to CN115) with the audio probe and amp. shows both Left and Right tones at those points, yet only the Right signal gets to CN115 pin 15. The Left signal does not get to pin 17. I have therefore soldered a link between the Left Test Point and CN115 pin 17. Both VAUXL&R now arrive at CN115.Now to HDMI B'D and Schematic diagram on page 126 in the Service Manual. We pick up the L&R Signal tones (now called ADINL and ADINR) on CN2 pins 30 and 32. With the Audio Probe I now follow these tones through to IC30 which is the Stereo A/D Converter (see page 159 in the Service anual).This is where my Audio Probing stops as the L&R signals are digitised from here on.So I must now find the IC which converts the signals back to Audio in order to proceed.Michael UK 11:29 GMTMichael UK 14:08 GMT

author: Studio1@29
author_rank: Contributor
timestamp: December 18, 2017, 06:07:38 pm
content: Continuing the test tone probing of VAUXL. See: Audio Video B'D page 103. With the AVR re-assembled on the bench, Different signal tones injected into VAUXL&R the results were: R Channel only at Speaker Terminal. Examination of foil side of Audio Video B'D, just 33mm from the front edge are two solder test points. One is for A/D_L and the other for A/D_R. I found continuity between A/D_R test point and CN115 pin 15. There was no continuity between A/D_L test point and CN115 pin 17. Therefore I soldered in a Jumper between these two points of A/D_L. The test tone for the VAUXL now gets as far as IC30 - the AD converter (as does the test tone for the VAUXR)Michael UK 18:08 GMT

author: Studio1@29
author_rank: Contributor
timestamp: January 10, 2018, 05:02:32 pm
content: Return to problem in Denon AVR-1912 after Christmas and New Year break. The problems have intensified and now signals only get to the HDMI B'D at the Ribbon Cable connector. Also had a problem on the SMPS B'D where the Power Supply to the Primary winding plocketry had come adrift from the pcb. After resoldering the male Primary plug to the pcb I had to install a strap to the fuse on the foil side to get power to the main Xfmr. I have invested in a FeelTech FY3200S Dual Channel Arbitrary Wave Function Signal Generator to replace my ageing and suspect Audio Signal Generators. The micro CD that came with it was useless as a User Manual, but FeelTech technical Very Rapidly (within an hour) sent me an email with a pdf attachment which gives all one would ever need to know about this Sig.Gen.Unit. M.Zacharius is so right about the possibility of broken solder joints and dodgy pcb's in this Denon AVR-1912. Now I have to trace those two signals and find out why and where they've stopped. Michael UK 17:00 gmt.

author: Studio1@29
author_rank: Contributor
timestamp: January 17, 2018, 12:06:49 pm
content: Hello, mzacharius -I have tried sending the problems I am experiencing to this Forum but am getting no replies, so I wondered if you, who have been so helpful, could shed some light?In order to make tests and keep the pcb's connected to preserve their electronic integrity, I have been experimenting soldering 'Tagged Test Tails' to various pins of the various connector blocks so that the conditions at those points can be measured with the AVR powered up.Currently I seem to have Voltage problems which are causing the Two Test Tones I am injecting into AUXL and AUXR to not get through the AVR.For example:(1) the +8V. rail at pin (1) CN101 (see p.110 of Service Manual) should read +8V. But it reads: +10.78V. on my dvm.(2) the +8V. at pin (14) CN14 (see p.111) should also read +8V. but it reads: +4.589V.(3) the Positive Power (see p.114), to the IC801: pin (30) should read: +7V. but it reads: +3.83V. (by Using an Endoscope and a long, sharp, bent probe this is just possible!)Have you any suggestions to forward this repair, please? Do you approve of my 'Tagged Test Tails' approach? If so, would you suggest attaching 'Test Tails' to other points for scrutiny? for I am at a stand still!Really I am a 'Beginner' and realise I should have entered myself as such - but at over 80, where does one 'begin'! (or, indeed, stop?)Michael UK

author: Zucca
author_rank: Unknown
timestamp: January 17, 2018, 03:37:41 pm
content: Studio1@29please continue to post your analysis, the replies will come for sure. It would be helpful if you could copy-paste some service manual schematics with your finding marked in it.Imagine a lot of EE looking jumping here, if they see a circuit with some measurement or real pictures they will be more attracted and interested to follow your steps.For example:https://www.eevblog.com/forum/repair/hp-34401a-error-612-613-615-617-618-619-621/msg489595/#msg489595

author: mzacharias
author_rank: Frequent Contributor
timestamp: January 17, 2018, 08:45:53 pm
content: Quote from: zucca on January 17, 2018, 03:37:41 pmI replied in this thread.https://www.eevblog.com/forum/repair/denon-avr-1912-e2ea-8v-wrong!/

author: Studio1@29
author_rank: Contributor
timestamp: February 01, 2018, 07:43:03 pm
content: So I took a long, hard think about this loss of Left Audio and did more tests in my Lab. And I discovered something very basic. The tone was not getting through to the SPKR for a very good reason - the cable CX4 has two broken conductors in it!! Interestingly this 40 way ribbon cable (pitch is 1mm) is removable at both ends - each end being identical in that they 'crimp' into place and use plastic grab tags which are attached to the printed side. So I totally removed CX4 ribbon, weighed it down on the bench to stop it from skittering about under test, applied the Ohm Meter a Uni-T (UT61E) dvm using sharp probes of thick piano wire which I ground down to a tapered point and attached to the probes by those plastic housed contact connectors which are available in strips of 10 or so on-Line. I discovered that CX4 contacts 5 (A-7V) and 8 (VAUXL) were broken. Hence the loss of the Left Audio. I therefore removed the grab-tag from the HDMI_B'D end where the breaks are (it tore off quite readily) and took my pair of carpet shears and brutally cut off this ribbon at the first crease. Then I put a thin line of CA glue along the end of the cut-off ribbon (on the printed side - like the other end) and attached the grab-tag, squeezed out and mopped up any excess CA glue, and weighed it down with a heavy hunk of bull-head rail (which I also use as an anvil) It is now gluing in place and should be fully cured by now. The next step is to reveal those 40 contacts in a very delicate way so none of them get nicked or cut. I don't know any realistic way to do this - so if anyone does, I would appreciate a description of the method.By the way, the Service Manual for the Denon AVR-1912 E2/EA and others, Ver.6 is available to down-load here:Denon AVR-1912 | Electrical Connector | Insulator (Electricity) - ScribdThanks for reading this. Michael Studio1 UK 19:42GMT

author: SoundTech-LG
author_rank: Frequent Contributor
timestamp: February 01, 2018, 10:19:08 pm
content: Several lengths and flavors available here:https://www.ebay.com/itm/2Pcs-AWM-20624-80C-60V-VW-1-40-Pin-1-0mm-Pitch-300mm-FFC-Flexible-Flat-Cable/252286710690?hash=item3abd75b3a2:g:TxEAAOSwPc9WwAw6