Denon 3808 - No Display / Audio Output

[crashp3]

Re: Denon 3808 - No Display / Audio Output

Could just be dust. Also be wary of some meters with continuity. Often show it for far higher than you expect. Retiredcaps says some do it at up to 1,800 ohms!

Wow! Definitely not dust, unit actually looks brand new! That coloration you see is definitely internally, not on the exterior. Thinks i'll just replace it to be on the safe side, whats a few bucks lol

[selldoor]

Re: Denon 3808 - No Display / Audio Output

Just measure it for now - meter on ohms 200 what reading does it give -probe on each end of the fuse with it off the board..

[crashp3]

Re: Denon 3808 - No Display / Audio Output

Meter on 200, fluctuates between .4 and .5, but predominatenly on .4

[selldoor]

Re: Denon 3808 - No Display / Audio Output

Most people would consider that a good fuse.

[crashp3]

Re: Denon 3808 - No Display / Audio Output

Alright, first off, thanks again for all your help thus far.

I was finally able to pull out the main power board (what a PITA!) to get to the relay. I've removed the top cover of the relay to make it easier to see what's going on. This is RL401.

I'll work on bypassing it, just wondering if there's a different way to test the relay? Once it's bypassed, due to the intricate design, I am thinking I'll have to completely reassemble to test.. blah!

Once again, I apologise for the poor pictures. I should have my DSLR back any day now.

[crashp3]

Re: Denon 3808 - No Display / Audio Output

Did a litle more testing, there is a secondary (identical) relay on the board for the secondary transformer. I took 8v across the known good relay (for the secondary trans) and I can immediately hear the relay clicking.

When I put the 8v across suspect (RL401) there is no clicking, only a spark.

Shorted coil? Would a relay just fail, or could it have failed due to other problems?

While it is apart, I've been reading about SMQ capacitors (which are on the power board) and have read mixed reviews. Would it be worth recapping to a different, more reliable capacitor? Thoughts?

[tom66]

Re: Denon 3808 - No Display / Audio Output

It's possible, though make sure the 8VDC source can drive that coil well (i.e. low impedance, it may be a low sensitivity coil.)

[crashp3]

Re: Denon 3808 - No Display / Audio Output

It's possible, though make sure the 8VDC source can drive that coil well (i.e. low impedance, it may be a low sensitivity coil.)

Well, back to the drawing board. I pulled the relay out of circuit (to bypass it) and while out of circuit, I tested it again with 8vdc, and it is now clicking. Ugh!

So, while the relay is tested in circuit, it doesn't click, out of circuit, appears to work fine.

[crashp3]

Re: Denon 3808 - No Display / Audio Output

Update, visually inspected the board more. There is a very small and minor hairline crack (indicated by the line in my picture) that went right through the relay (RL401) and D412. Likely from the dismal drop.

Relay pulled out of circuit, the board still showed a circuit.

Remove diode D412, tested, and it tested bad. With D412 removed, the board does not show circuit across RL401, where it previosly (and shouldn't) have had a circuit.


Testing the few other parts in circuit, but I am hopeful!

[selldoor]

Re: Denon 3808 - No Display / Audio Output

Is it a DLS1U like the one in the picture - if so, shouldnt you be testing with 6 volts?

[crashp3]

Re: Denon 3808 - No Display / Audio Output

Is it a DLS1U like the one in the picture - if so, shouldnt you be testing with 6 volts?

Same exact one. Yes, definitely 6 volts, but all I had was 8.. and was frustrated

[tom66]

Re: Denon 3808 - No Display / Audio Output

Well, for some reason the relay isn't being triggered. Check R402, and the diode across the coil.
Edit: NVM, saw your above post.

[newbiesat]

Re: Denon 3808 - No Display / Audio Output

Hi crashp3,
Try to replace transistor TR402 (KTC3199) to see what happen? Maybe it's a bad transistor?... Also, do you have DENON 2307CI service manuals? If you do, could you please share it in the dropbox. Thanks.

[crashp3]

Re: Denon 3808 - No Display / Audio Output

First off, wanted to thank everyone for help thus far!

The new diode came in today (D412) and I replaced it but still no luck. I double checked the board repair from the other day, and that's holding up fine.

I jumpered over the relay tom recommended after replacing the diode.. and it works perfectly fine when jumpered! The main transformer kicks in, front display fires up, and it now outputs sound!

Now it's time to figure out why the relay isn't clicking over. Eventhough I performed a "test" on it, I ordered a new one with the diode, but the relay is on backorder for atleast 2 weeks and I've had no luck finding a comparable replacement

I'll look into TR402 tomorrow, and am definitely open to any other suggestions.

newbie: my typical source doesn't have access to Denon manuals, I actually bought (sigh) the PDF copy of the 3808 manual from some online vendor for $5. I couldn't find yours either, for free that is.

[budm]

Re: Denon 3808 - No Display / Audio Output

What DC voltage do you get at Emitter and Base of TR401, 402? Emitter and Collector?

[nintari]

Re: Denon 3808 - No Display / Audio Output

just subbing to this as I have the same receiver (3808CI)

also had the similar issues happen with a 2808CI that was shipped to me and the front circuit board was destroyed. had a hell of a time getting the traces bypassed with wire, then the flat ribbon connector that went from the front panel to one of the other boards was off by just a hair so the pins didn't make correct contact, had to manually solder each of them and it finally worked.

Anyway hope you get this issue resolved! I'm curious to see what it is.

[gilly1984]

Re: Denon 3808 - No Display / Audio Output

If you have an identical amp and don't mind opening it take some readings and compare them together.

[crashp3]

Re: Denon 3808 - No Display / Audio Output

Still working on this one Just swapping out the powerboard would be easier, due to the crack, etc. but Denon doesn't seem to like to sell a complete spare board, unless you're willing to give them your first born.

Working on it is also tough, they maximize every square inch of space in here, and removing the power board consists of removing the main HDMI/processor board, a secondary power board, and then the main power board.. not including about 24 screws. 4 daughterboard bridge connectors, and over 10 electrical connectors.

I'll have more results come tomorrow or the following day

[crashp3]

Re: Denon 3808 - No Display / Audio Output

What DC voltage do you get at Emitter and Base of TR401, 402? Emitter and Collector?

Got around to testing it out earlier today. Sorry for the delay, disassembly isn't easy and life priorities always get in the way of fun!

TR402 (KTC3199 - one for the main power trans that isn't functioning)

Emitter: .009vdc
Conductor: .006vdc
Base: .67

TR401 (KTC3199 - one for the standby trans that IS working)

Emitter: 0vdc
Conductor: .13vdc
Base: .75

Datasheet for transistor:

So the parts are the identical ones, but voltages (aside from emitter) are different. Any help is appreciated!

[crashp3]

Re: Denon 3808 - No Display / Audio Output

Just wanted to update. The problem has been fixed! I replaced both the relay and TR402, reassembled, and problem fixed!

Thanks to everyone for the assistance here!