I just put the finishing touches on my HK730 rebuild. (new caps, replaced problematic transistors, reseat power transistors, idle current adj., repaired stereo lamp circuit, rebuit phone bd. to RIAA. replaced front panel lamps, Deox treatment of switches and controls. ) It's in minty condition inside and out. Here's some observations and screw ups along the way:
1. Dlucy's mega thread form 2019 was a huge help. Thanks to Dlucy and all the contributers!!
2. I had minimal problems sourcing the BOM lists from Mouser. The only issue is that most of the UKL caps are EOL. (For the signal path I substituted Panasonic FR, Rubycon TWL and Nichicon MUSE where they fit)
3. The only problem with this receiver was a bad stereo indicator lamp AND a bad HA1156 FM demod I.C. FM stereo worked great but the I.C. wouldn't turn on the lamp. This is the second time I've had to replace this I.C. (Pioneer SX737 was previous). Is this I.C. and known problematic component? Fortunately they're still avail. on Ebay.
4. I chose 5600uF/63V PSU caps. Spreading the tabs worked but barely enough protrusion to solder onto the pads.
5. I rebuilt the power supply/tested and then moved on to power amp. Upon testing I thought I "bricked" this unit. No sound either channel. After a cup of coffee and re-reading the schematic I realized I got the power transistors out of order during cleanup and heat sink work. When properly reinstalled everything worked great.
6. Now was a great time to adjust idle current but I could only get 5 mV. Then realized I needed to plug it into full line voltage vs the dim bulb tester.
7. The preamp and tone bds were a PIA to access but I got thru it and only had to unsolder the headphone jack.
8. Cleaning the controls was pretty easy. With the unit positioned on it's back, Deoxit could be drawn into the switch cavites via gravity and capillary action. (no need to take them apart or drill access holes in them). The gap where the button enters the control has enough gap to accept cleaners. I did two phases with each phase using QD, D5 and D100. Complete success.
9. The tuner bd. was a PIA because it's so packed with components you have to guess where to desolder on the backside. I really had no problem with the control shaft in the way. There was enough room under it to work. The copper shield was easy to unsolder to get to the one capacitor under it.
10. The phone bd was a lot of components to replace for a full RIAA rebuild but it was successful. I almost forgot the two 5.6K resistors that needed to be attached to the backside of the bd.
It's complete and sounds great.
1. Dlucy's mega thread form 2019 was a huge help. Thanks to Dlucy and all the contributers!!
2. I had minimal problems sourcing the BOM lists from Mouser. The only issue is that most of the UKL caps are EOL. (For the signal path I substituted Panasonic FR, Rubycon TWL and Nichicon MUSE where they fit)
3. The only problem with this receiver was a bad stereo indicator lamp AND a bad HA1156 FM demod I.C. FM stereo worked great but the I.C. wouldn't turn on the lamp. This is the second time I've had to replace this I.C. (Pioneer SX737 was previous). Is this I.C. and known problematic component? Fortunately they're still avail. on Ebay.
4. I chose 5600uF/63V PSU caps. Spreading the tabs worked but barely enough protrusion to solder onto the pads.
5. I rebuilt the power supply/tested and then moved on to power amp. Upon testing I thought I "bricked" this unit. No sound either channel. After a cup of coffee and re-reading the schematic I realized I got the power transistors out of order during cleanup and heat sink work. When properly reinstalled everything worked great.
6. Now was a great time to adjust idle current but I could only get 5 mV. Then realized I needed to plug it into full line voltage vs the dim bulb tester.
7. The preamp and tone bds were a PIA to access but I got thru it and only had to unsolder the headphone jack.
8. Cleaning the controls was pretty easy. With the unit positioned on it's back, Deoxit could be drawn into the switch cavites via gravity and capillary action. (no need to take them apart or drill access holes in them). The gap where the button enters the control has enough gap to accept cleaners. I did two phases with each phase using QD, D5 and D100. Complete success.
9. The tuner bd. was a PIA because it's so packed with components you have to guess where to desolder on the backside. I really had no problem with the control shaft in the way. There was enough room under it to work. The copper shield was easy to unsolder to get to the one capacitor under it.
10. The phone bd was a lot of components to replace for a full RIAA rebuild but it was successful. I almost forgot the two 5.6K resistors that needed to be attached to the backside of the bd.
It's complete and sounds great.
