Hi there! I do not see the trace side of the "Power Supply Tuner - Preamp Board" very clearly, but it seems, most likely, that the circuit has been previously modified according to "Service Bulletin #165" issued in Aug. 1974. If the orange lead is connected between the collector of the TR801 (small transistor) on this board and the positive terminal of the C904 (one of the main filtering capacitors) - then for sure it is modified. In this modified circuit, the "missing" capacitor and "missing" diode are not active any longer and can be removed all together (and even the second diode, too). Then again, you've got yet another issue with burned power transistor (large one) for voltage regulation, which caused hum. That one you've managed just fine! Congrats with a good job of keeping alive this piece of a genuine vintage High Fidelity and GOOD LUCK with other vintage projects!
Thank you so much for posting this. I think I have the same problem with my 630 and I will pursue the right fix now! Those Titans are fantastic little speakers, aren't they? Can't believe how much sound they put out.
I have a 930 that looks very similar to your 630. It has output issues. DC offset measured at speaker posts are 130mv and 70mv, and keeps on blowing speaker fuse. Visually everything looks good on the power amp part. Preamp and headphone both work well. What's the most likely cause for this? Varistors? differential pairs? Thanks!
Have you check the bias of the power amp? If they are high, it will cause blowing fuse. Use the same method shown as in my video to adjust VR601 and VR621 to see if you can adjust the reading to 10mv. Please send me the answer and photos to my email: audiophileedh@gmail.com. I am glad to help you to figure out.
Hi there! I do not see the trace side of the "Power Supply Tuner - Preamp Board" very clearly, but it seems, most likely, that the circuit has been previously modified according to "Service Bulletin #165" issued in Aug. 1974. If the orange lead is connected between the collector of the TR801 (small transistor) on this board and the positive terminal of the C904 (one of the main filtering capacitors) - then for sure it is modified. In this modified circuit, the "missing" capacitor and "missing" diode are not active any longer and can be removed all together (and even the second diode, too).
Then again, you've got yet another issue with burned power transistor (large one) for voltage regulation, which caused hum. That one you've managed just fine!
Congrats with a good job of keeping alive this piece of a genuine vintage High Fidelity and GOOD LUCK with other vintage projects!
Thank you so much for posting this. I think I have the same problem with my 630 and I will pursue the right fix now! Those Titans are fantastic little speakers, aren't they? Can't believe how much sound they put out.
Don't let the size of these Titans fool you. I have been using them on my demo video. They are one of my favorites.
My receiver still here 1972 still working
I have a 930 that looks very similar to your 630. It has output issues. DC offset measured at speaker posts are 130mv and 70mv, and keeps on blowing speaker fuse. Visually everything looks good on the power amp part. Preamp and headphone both work well. What's the most likely cause for this? Varistors? differential pairs? Thanks!
Have you check the bias of the power amp? If they are high, it will cause blowing fuse. Use the same method shown as in my video to adjust VR601 and VR621 to see if you can adjust the reading to 10mv. Please send me the answer and photos to my email: audiophileedh@gmail.com. I am glad to help you to figure out.
looking for a selector knob for this model any idea the bay has nothing
It is hard to find them. I suggest continuing to check out in ebay.
Comment l'a tu démonté? Car la mienne à aussi un problème
Can you write the question in English?