Denon AVR-X2000 trials & tribulations

[re-atari]

Hi all,

A few weeks back I picked up a defective Denon AVR-X2000 from an online marketplace similar to Craigslist. Seller replied to my mail inquiry that all of a sudden the receiver didn't respond to the on-off switch anymore, it appeared to be totally dead. Only when picking it up, he told me he had opened the case, but as he hadn't found anything visibly damaged, just closed it back up and decided to get rid of it.

If that wasn't enough to walk away (I don't like to take on stuff where someone has already been inside), the calibration mic and remote were missing. But since I was there at his front door and the asking price was fairly decent, I decided to take it home with me anyway.

My procedure with stuff needing a repair, is to first open the case in order to check for components with visible damage instead of just connecting it to the mains to 'see what it does or doesn't do'. A visual inspection revealed one of my worst nightmares. Either the seller or a service center had done an attempt to assess and fix the fault and failed miserably.

Here's a list of what I saw inside the receiver.

1. The standby PSU pcb was severely bodged.
- apparently the 'repairman' had tried to disconnect connector CP4142 from its socket, but failed to realise this requires pushing in a locking tab to free it before pulling it out. As a result the plastic socket was pulled up from the pcb. From the damage on the solder side of the pcb it looks like he then concluded he couldn't get the connector to come loose, so just pushed it back down. And in doing so, put so much pressure on the metal connector pins, that one of them sheared the copper track free from the pcb, and tore the track as well just for good measure. All along the motto: if you don't succeed, you're just not trying (or pushing) hard enough...
CP 4142 is the connector that carries one of the primary wires to the transformer, the receiver is switched on/off via this wire by the standby relay, so no surprise the torn pcb track made it appear 'dead'.

- several components were desoldered and put back in, presumably to do some testing/measurements. Sadly this desoldering had resulted in a number of tears in copper tracks, which were fixed quite crudely (bridged with pieces of wire). Well, all but one, a track from IC 4143 (KIA 2431, TL431 compatible) to C4155 was overlooked, resulting in a partially disconnected adjust line.

- besides that, the soldering job putting the desoldered components back in was done quite poorly. Bad solder joints, et al.

- caps are of a known sub-par brand (Samyoung NXA), 3x 5600uF/6,3V, 10uF/50V and 47uF/25V. I think they are the original factory installed ones.

2. the HDMI pcb was missing a few components.
On the 5,2V standby voltage line there were 2 SMD filtering caps C3789 and C3802 (both 470uF/6,3V) removed. The reason for this is not clear, but the removal was quite crudely done. Both caps were simply broken off their pcb pads. Looks like the repairman read one of the threads on Badcaps about failing Onkyo HDMI boards, where it was indeed suggested to just break off failing SMD caps. Why he didn't install new caps is a mystery to me. What's worse, when removing these 2 caps he managed to shear off an adjacent component (L3628, SMD ferrite bead). On closer inspection of the pcb, this missing component turned out to be laying between the pins of nearby connector N3401.

3. connectors on one of vertical pcb's weren't properly lined up to be inserted in the respective sockets on the main PCB. The repairman didn't notice this, but did tighten the screws in the burring hole clamps, resulting in them both sheared out of their soldering holes. And the connectors deformed of course...

4. several flatcables were not connected. The flatcable going to the front USB-connector and the flatcable carrying the DC and thermal protect signals were hanging loose.

5. deposit on a number of pcb's indicated that a few drops of a soda drink (Cola by the looks of it) was spilled and had leaked inside.

6. add to that transport damage on the front cover in the left below corner.

By the looks of it the repairman added some damage to the original fault, and decided to just give up and declare it a total-loss.

I decided to fix the above faults and see where it got me. The service manual is a great help, containing very clear pix and a nice faultseeking flowchart. It looked like it would be mission impossible, though, where to begin? OK, just do it, start with disassembling and cleaning it.

Next came fixing the socket and broken tracks on the standby PSU, I did a resolder on all components (incl. SMD's on solder side) and measured all components in circuit. They all appear to be OK. I left the Samyoung caps for now, as my ESR meter showed they are good. I measured them in circuit, though. As I get the specified 5,2V standby voltage, I think they are OK.

Then I replaced the missing caps on the HDMI board with standard axial ones (470uF/16V). After measuring the component found between the adjacent socket pins, it's highly likely this is in fact L3628, so resoldered it. This component sits in the line between CPU and Standby PSU, that according to service manual carries the signal to get the receiver out of standby (MAINPWR). After resoldering, there's continuity on this line.

Resoldered both burring hole clamps and connected the loose flatcables.

I then removed the dried Cola deposit, turned out to be just a few drops here and there. Sadly also in a 'dangerous places' where 70V goes to the vertical 7ch amp. Hopefully the damage isn't there.

I carefully reassembled the pcb's, making sure all connectors were properly inserted in their sockets. I´m pretty sure I now restored the receiver back to the situation it was in before the 'repairman' got his hands in.

After connecting the receiver to the mains, the fault immediately became clear. It wakes up, relay clicks, activity led is green, display shows 'AV SURROUND'. But it seems to be rebooting after 1 sec, relay clicks, green led goes out and comes back on, display gives same message. The led never turns red, so probably there's no protection error. This situation goes on and on until I disconnect the receiver from the mains.

Error checking I did so far:
- measured voltages. The regulators on the mainboard are OK, and 5,2V Standby voltage to HDMI board is present. I haven't desoldered and measured the bridge rectifier (D10SB60) on the mainboard yet. My guess is it's all right, as I wouldn't get correct voltages on the regulators if it fails. All fuses are OK.
- removed connector CP4000 from transformer to mainboard. Same fault behaviour.
- removed connector carrying DC and thermal protection signals. Same fault behaviour.
- measured DC on every loudspeaker clamp, it's below 1 mV on each.
- measured every coil on transformer, there's continuity on each (so thermal fuse OK). I haven't measured their inductance with my LCR meter yet.
- inserted headphone plug. Same fault behaviour.
- tried CPU reset and network reset. Didn't work. Same fault behaviour.
- tried entering 'protection history mode'. Didn't work. Same fault behaviour.

So, still some measurements to do. Hopefully the fault isn't due to a defective CPU.


Does anyone have suggestions for further measuments, or even an idea what might be going on here? Any input is greatly appreciated.

re-atari

[re-atari]

Re: Denon AVR-X2000 trials & tribulations

I had a chance to do some further investigations on this receiver yesterday evening.

I decided to desolder the SamYoung NXA caps on the Standby PSU pcb, in order to measure capacity and ESR out of circuit. As I expected, all were OK, capacity was nearly spot on and ESR around 0,05 Ohm. I already had a steady 5V standby voltage before, so now made sure the fault isn't located here. It also confirms I managed to fix the defective tracks on the Standby PSU pcb. The 5V standby voltage is present on both caps that I soldered on the HDMI board to replace the missing ones, so that's fixed as well. I had already measured the power transistors last week, none were shorted.

Now, where to go next? As I descibed in post 1, inspection of the various pcb's indicated the previous owner might have spilled a few drops of cola. One of the drops had fallen precisely on a connector on the mainboard that carries +60V and -60V to the vertical 7ch amp pcb. I had already cleaned this connector last week, desoldered and put it in a glass of water for some time to desolve the dark brown sugary deposit. The mainboard had a slight bit of this deposit as well, was easy to remove with a damp cloth. I measured the voltages on this connector yesterday, but it revealed nothing out of the ordinary, both +60V and -60V were present. This tells me the bridge rectifier is OK.

Decided to check the DC and thermal protection circuit next. The service manual indicates a fault if the DC protect or thermal protect signals from the 7ch amp board to CN3405 on the HDMI board are +0,6V or -0,6V with the receiver switched on. There are 2 DC protect lines and 2 thermal protect lines on CN3405. Both DC protect signal lines stayed around 0V, so no problem there. This makes sense, as I had already measured for DC on each of the loudspeaker clamps last week, and found none then.

Both thermal protect lines on CN3405 on the other hand rose to just about +0,6V after switching on, so looks like something's not OK here. Signal line 'TR Thermal' monitors the C, FL, SR and SBL amp, signal line 'RADI thermal' does the same for the FR, SL and SBR amp. Strange that both lines indicate a fault situation.
I disconnected the power supply lines from the mainboard to 7ch amp board, but the error situation described in post 1 remained. Disconnecting connector CN3405 on the HDMI board made no difference either. Strange enough now each DC and thermal signal line stayed around 0V after switching the receiver on. Looks like the fault is not on the 7ch amp pcb after all?

I studied the schematics to trace both thermal protect signal lines in the service manual, but can't make any sense of what might be wrong. Or even if they are the cause of the receiver's error behaviour in the first place.

When the receiver is switched on, there are no components that start to smoke, and there's no 'electrical' smell either. The IC's on the HDMI board do not warm up at all. So, no dead give aways of what's (not) going on.

At this moment I'm stumped. I'm open to suggestions what to check next!

re-atari

[re-atari]

Re: Denon AVR-X2000 trials & tribulations

I finally got this receiver fixed and up and running again. Turned out the fault was in the standby PSU. I got an identical PCB on loan, by doing measurements on both PCB's and comparing them I found a mosfet had failed. After desoldering and measuring it, the values showed it was indeed defective. They simply were not how a mosfet should typically read. I didn't do any measurements to the standby PSU live connected to AC, though.

It turned out this mosfet (KMB2D0N60SA) is not a commonly available type. With the help of an online cross-reference search engine and some input in this thread https://www.badcaps.net/forum/showthread.php?t=67598, I managed to find a drop in equivalent type (Vishay Si3208BDS).

After soldering in the replacement mosfet I did some final measurements on both the mosfet and the surrounding components. Readings on the mosfet were as they sould be, but all of a sudden resistor R4145, value 1M and connected between the mosfet's Gate and Source (probably as a protection for the mosfet), read open circuit. I measured its nominal value a few weeks earlier. After desoldering, it still read open circuit, so had to be replaced as well. In retrospect I think this resistor was already flaky, and this was the reason the mosfet had died in the first place.

I really didn''t want to go through the trouble of online ordering a single SMD resistor, so just used a standard type I had in my spare parts box. It took a little effort bending both wires and soldering them in place.

After switching it on, the receiver immediately came to live without a problem, where it had been locked in repeatedly switching on and off previously. The receiver has been test running just fine all evening. No overheating, no strange clicking of the STDBY relay, no 'electrical' smell. Looks like a result to me

re-atari