Onkyo TX-SR607 overheating after repair - Page 1
Forum section: electronics / repair

author: stojke
author_rank: Regular Contributor
timestamp: January 24, 2018, 09:25:43 pm
content: Hi. There is an Onkyo TX-SR607 that upon arrival would shut it self off after 15 to 20 minutes of operation with overcurrent error message. Upon lick finger and touch inspection it was concluded that only the R speaker side of output transistors were getting warm and the second portion of the heatsink was lukewarm.I initially, after seeing that they were already replaced before, decided to test the capacitors and found out they were pretty dodgy (1/3 of value down) and have replaced them with a new set of 470uF 16V ones (5 of them that were already altered, seen from all the resin residue). After a few tests, since replacement, with 5 speakers (Onkyo original speakers , 6 ohm , L R SR RL C) it shutdown when playing, was turned on in a few seconds and shutdown with out any music being played. At that point it was left off for a few minutes and turned on to see smoke coming out of it after a few seconds (Near the R channel).Cause of the smoke were burned output transistors Q6061 (2SC5242) and Q6051 (2SA1962) as well along them a burnt resistor array R6101 (2x0R22 5W). On the preamp side Q6011 (2SC1740S) was blown as well as resistors R6021 (2.2ohm 1/4W) and R6071 (82ohm 1/4W). Q6044 (2SC1930) seems a little dodgy judging by my Shenzhen transistor tester as it reports an B (Amplification ?) rating of 135 while other 2SC1930 report an B of 165, multimeter diode mode testing show the same (Variation by 1%) result as others in the rest of the circuit (7x same preamp stage (At least I think this is an preamp)).I have replaced those with an replacement type 2SC5200 for 2SC5242 (Q6061) , 2SA1943 for 2SA1962 (Q6051) , two times 0R22 5W as one 2x0R22 5W resistor array (R6101) and an BC547C for 2SC1740S (Q6011) (2R2 and 82R stayed the same).After replacing all that I decided to check (Much too late) my speakers, and to my expectation the right speaker blew , 0hms even his mama can't recognize him now.I decided to continue the test with only 4 speakers now (L SR SL C) and thats when we arrive at the current problem - The receiver is overheating. The heatsink gets so hot i burned my hand from touching it.Is it possible that the first failure was due to something else beeing broken? Or is this caused by me altering the preamp stage of R channel? Please help.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 25, 2018, 02:41:52 am
content: https://elektrotanya.com/onkyo_tx-sr607_sm.pdf/download.html

author: mzacharias
author_rank: Frequent Contributor
timestamp: January 25, 2018, 01:32:14 pm
content: The original failure of the output transistors is quite common and could easily have been caused by either shorted speaker wires, or continuing to try to use the receiver while it was exhibiting clear signs of failure; shutting down after playing a while, etc.

author: wraper
author_rank: Unknown
timestamp: January 25, 2018, 02:09:55 pm
content: Apparently you did not even try measuring voltages/currents (voltage drop over resistors) in circuit.

author: stojke
author_rank: Regular Contributor
timestamp: January 25, 2018, 05:27:33 pm
content: Sorry for not mentioning, but this is my first time repairing something like this.I repaired laptop and desktop components only (Not on an engineering level).How would I do proper measurements?Where to connect ground where to connect positive probe? What to look for there anyway??

author: mzacharias
author_rank: Frequent Contributor
timestamp: January 25, 2018, 11:07:19 pm
content: In the example of the front right channel, a DC millivolt reading should be taken across R6100, a dual package 0.22 ohm 5 watt resistor. A normal reading across the pair might be in the neighborhood of 10 to 15 mill-volts. This assumes the resistor on your channel in question is still good.The 2SC1740 bias transistor should be carefully checked, as well as related parts.I think the driver board is detachable. There will be a driver section for each amp channel. They will be identical to each other. The individual transistors,resistors, etc need to be checked as there is likely damage here as well.Checking voltage with respect to ground simply means connecting the (usually negative) lead of the multimeter to chassis ground.Good luck and all, but I think perhaps you may be in a little over your head on this one.