Onkyo A-RV401 can't find resistor on schematic - Page 1
Forum section: electronics / repair

author: onedumbquestion
author_rank: Contributor
timestamp: July 29, 2023, 09:01:39 pm
content: Resistor R552 is shown on the board but not the schematic I know it's supposed to be there cause it burned out and I'm trying to replace it This is a link to an image of the resistorhttps://imgur.com/a/j4MVqxFand here see 2 dark holes where the board is marked R552 is where I removed it fromhttps://imgur.com/a/3KBaQoU

author: Kim Christensen
author_rank: Super Contributor
timestamp: July 30, 2023, 02:39:12 am
content: Why not just look at the other channel? It should have the same value resistor in a similar location.EDIT:The reason you don't see it on the schematic is that they only draw the left channel and have the note: (Rch: Same as Lch) on the drawing. But it's listed in the parts list as 8.2 ohm 1 watt. Odd that it's burnt since it's in series with a capacitor forming a zobel network across the speaker output. So check that capacitor for a short ( C528 0.047uF @ 50V ). If the capacitor is OK, it is possible that the amplifier became unstable and oscillated at a very high frequency.The capacitor voltage rating seems under rated since the output has +-62V supply rails! I'd replace C527 & C528 with 100V or better.Left = R551 & C527Right = R552 & C528

author: SpecialK
author_rank: Regular Contributor
timestamp: July 30, 2023, 04:18:12 am
content: Pictured resistor seems to be 2 kohm or 2,2 kohm resistor

author: Shonky
author_rank: Frequent Contributor
timestamp: July 30, 2023, 08:16:11 am
content: Quote from: SpecialK on July 30, 2023, 04:18:12 amDisagree. You're reading from the wrong end. The larger gap would indicate a tolerance band. The other dark band does look black in the photo but the photo is not great. Grey red gold from the right to left in the image with a 2% tolerance would line up with the BOM.Find R551 and compare.

author: eurgenca
author_rank: Regular Contributor
timestamp: July 30, 2023, 04:30:58 pm
content: I don't think this is a 1W resistor. Better picture will be nice. What is dark spot on green resistor?

author: SpecialK
author_rank: Regular Contributor
timestamp: July 30, 2023, 05:29:14 pm
content: What was the initial problem with the unit? Distortion, or a channel completely out? I can't help but think some transistors have perished.

author: Kim Christensen
author_rank: Super Contributor
timestamp: July 30, 2023, 06:24:38 pm
content: Quote from: eurgenca on July 30, 2023, 04:30:58 pmIt does look awfully small. Too bad that the picture of the PCB is so blurry that we can't really see the silkscreen markings for ourselves.

author: Vovk_Z
author_rank: Super Contributor
timestamp: July 30, 2023, 11:57:09 pm
content: Quote from: SpecialK on July 30, 2023, 04:18:12 amIt looks like 1k for me.

author: Shonky
author_rank: Frequent Contributor
timestamp: July 31, 2023, 02:34:30 am
content: I have no idea how you can get 1k that out of the picture. Nothing lines up with your read of the colours.

author: elecdonia
author_rank: Frequent Contributor
timestamp: August 09, 2023, 08:13:24 pm
content: I agree with the post stating R552 is 8R2 ohms (8.2 ohms). Reading from right to left (as shown in OP photo) the bands should be gray, red, gold. The overheated area makes it difficult to see the gold band. The red band at the left end indicates 2% tolerance.The resistor in the OP photo seems extremely small for a 1 watt rating. It could get overheated and discolored just by passing a large amplitude 20kHz signal through the amplifier. As recommended in the other post, replacing R552 with a 2 or 3 watt rated metal oxide resistor would be a good idea, and also replacing the original ceramic disc capacitor C528 with .047uF film capacitor rated at 100V or higher. This should be done on both channels.I own the exact same model. Mine suffered a serious blow-up of one channel. It required replacing both large output transistors along with several resistors and small transistors. There was one small hole burned through the PC board. I was able to repair that. The other channel was undamaged.I don’t recall replacing R552 or C528 in my unit. I’ll look at my amplifier and post photos of these parts.I also have an original printed service manual. I’ll post relevant sections of the schematic as soon as I can.My impression of this amplifier is that it is a simple but excellent sounding integrated amplifier. The video switching section is irrelevant these days because it only supports analog composite video (yellow RCA jacks). But it has everything else that a decent quality 2-channel integrated amplifier needs to have on the audio side.Questions for OP:1) Did this amplifier have any other burned or damaged parts other than this one resistor?2) Is the amplifier working on both channels at this time?

author: Koray
author_rank: Regular Contributor
timestamp: August 18, 2023, 07:35:56 am
content: I hate it when somebody drops a question with little information and disappears.K.

author: Vovk_Z
author_rank: Super Contributor
timestamp: August 18, 2023, 09:26:41 pm
content: Quote from: elecdonia on August 09, 2023, 08:13:24 pmIt's much easier to guess when you have a schematic diagram or an amplifier PCB in your hands. Otherwise that's very non-accurate guessing.