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Nakamichi 730 Receiver Lamping?

j.phillip

j.phillip

New Member
Hi There AK community-- first posting(!) Have lurked for a couple years and have seen some great insight come up here -- I'm in need of a little help.

I just acquired a very beautiful Nakamichi 730 receiver, the design, build -- not to mention the sound -- is very enjoyable. I do have a couple function lights out, though (light behind "bass" , "treble" , "threshold" controls, as well as the "stereo" and "dolby FM" indicators). Has anyone here opened one of these up and replaced lights/lamps?

I have downloaded a service manual, but as far as I can see it gives no information on the replacements, procedure, etc. Searching AK, people have talked about fixing these up, but there's nothing specific. In any case, any info is sincerely appreciated! Before opening it up and potentially getting into a mess, I wanted to get any info I could. ((thank you))
 
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Hello. I have a 730 right now in my bench. The service manual I've downloaded has a very detailed disassembling procedure, several pages explaining how to remove each board and even the front and the lights.

Search for another service manual on line. I've downloaded from elektrotanya.com (no affilation )

Welcome to AK !
 
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elnaldo said:
Hello. I have a 730 right now in my bench. The service manual I've downloaded has a very detailed disassembling procedure, several pages explaining how to remove each board and even the front and the lights.

Search for another service manual on line. I've downloaded from elektrotanya.com (no affilation )
Click to expand...


Thanks for the reply -- I did download the service manual (from hifi engine?) and can see how to disassemble, but maybe I missed how the lights are attached (I'm assuming they are soldered?) and what to replace them with... I guess I just wondered if anyone knew off hand before I start opening up this fairly complicated beast! I'll have to look again at the manual
 
Just checked the parts numbers, Volume lights and the other light are not the same part, so probably different lamps.

Check page 55 and 56 (lamp pcb ass'y) , and page 61 62 (Volume lamp ass'y)
 
elnaldo said:
Just checked the parts numbers, Volume lights and the other light are not the same part, so probably different lamps.

Check page 55 and 56 (lamp pcb ass'y) , and page 61 62 (Volume lamp ass'y)
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Thank you. I actually have spares of that lamp you linked to (from a Yamaha amp re-lamping I did recently) , but I will have to check the spec on the other ones, see what may work well. I was hoping they were not soldered, but oh well, I 90% expected it. Definitely appreciated--
 
j.phillip said:
Thank you. I actually have spares of that lamp you linked to (from a Yamaha amp re-lamping I did recently) , but I will have to check the spec on the other ones, see what may work well. I was hoping they were not soldered, but oh well, I 90% expected it. Definitely appreciated--
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Hello . Did you manage to remove the lamp board? I need to replace 2 bulbs, but found impossible to do what the service manual says. Removing the screws described in the manual, and the board not even move 1/1000 from it's position. I suspect deeper disassembling is needed.
 
elnaldo said:
Hello . Did you manage to remove the lamp board? I need to replace 2 bulbs, but found impossible to do what the service manual says. Removing the screws described in the manual, and the board not even move 1/1000 from it's position. I suspect deeper disassembling is needed.
Click to expand...

I actually just left it alone because I only have 3 minor indicator lights out and felt like it's not worth the effort for right now. Were you able to get it apart? And were those bulbs you mentioned the right kind of bulb? I am saving changing them for some rainy day right now... I'm also a little leery of opening all that up and creating more problems for myself as it is working perfectly in all other aspects right now!!
 
I really like this receiver, btw. It is a powerhouse! Definitely the most powerful unit I've ever owned. The only thing I don't like are those tiny fine-tuning fm adjusters for the presets, to me they seem like they don't fit at all with the rest of the design.
 
I managed to open the front and reach all the bulbs.

The bulbs need to be 60mA (50mA at least), if not (this unit had 35mA bulbs at the Phono and Aux selectors), the function selector won't work. Actually the function changes, but due to the low current limited by the bulbs , the unit will stay in "mute" state, distorted and low level output.

The bulbs lighting the sliding potentiometers are not related to the circuit, those are 3 or 4 bulbs in a strip that you can remove sliding from one side. Desoldering and cutting/regluing a mask tape is needed to replace the bulbs. You need to loosen one very tiny screw and remove other 3 between the sliding knobs. I was miss-reading the service manual, removing larger screws at the bottom of the front plate.

The bulbs need to be 3mm, the smallest, not the 5mm bulbs that won't fit.
 
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elnaldo said:
I managed to open the front and reach all the bulbs.

The bulbs need to be 60mA (50mA at least), if not (this unit had 35mA bulbs at the Phono and Aux selectors), the function selector won't work. Actually the function changes, but due to the low current limited by the bulbs , the unit will stay in "mute" state, distorted and low level output.

The bulbs lighting the sliding potentiometers are not related to the circuit, those are 3 or 4 bulbs in a strip that you can remove sliding from one side. Desoldering and cutting/regluing a mask tape is needed to replace the bulbs. You need to loosen one very tiny screw and remove other 3 between the sliding knobs. I was miss-reading the service manual, removing larger screws at the bottom of the front plate.

The bulbs need to be 3mm, the smallest, not the 5mm bulbs that won't fit.
Click to expand...

Thanks for the run-down! That's interesting... I am taking it that the "Stereo" / "Dolby FM" / "Hi-Blend" / FM Mute grouping is similar to the function (phono / aux) buttons as far as the type of bulbs needed (?) ... something like a 12v 60mA grain-of-wheat 3mm bulb that gets soldered on
 
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Yes, all that strip has the same kind of bulbs, and most of them are electrically part of some transistor biasing circuit, so I'd stay with the original 3mm 60mA bulbs.

I've found 50mA bulbs locally, and they work. But the 35mA from a previous repair didn't.
 
elnaldo said:
Yes, all that strip has the same kind of bulbs, and most of them are electrically part of some transistor biasing circuit, so I'd stay with the original 3mm 60mA bulbs.

I've found 50mA bulbs locally, and they work. But the 35mA from a previous repair didn't.
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Right on, Thanks. I'll have to order some, all my spare bulbs around here won't work. Unhooked my 730 today to get to this soon.
 
bktheking said:
So is there a list for the lamps going ? I just bought one too and need to do so some lamp work.

Thanks
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Hello. You can use the mentioned 12v 3mm 60mA (or 50mA) bulbs. The volume dial can accept three 5mm bulbs but it's easier to buy all 3mm.

The volume and other slide knobs share 3 bulbs.

I'd say don't be too lazy and completely remove the front, even if you need to cut the wire ties and disconnect 10 connectors. The work is much easier that way. Take pictures of the connectors before disconnecting.
 
In case anyone else comes across this thread, the function bulbs are standard #7219 bulbs from Mouser. They are soldered in. If you delete D311, the “mute on burnt out bulb” function is disabled. Because of the required current draw, LEDs can not be substituted. And don’t forget to replace the 4 AA cells underneath with lithium AA to prevent them from exploding. They make a heck of a mess if regular alkalines are left in there too long.
 
For those who have the 730, is the 730 any good ? I have one with my tech, went from the seller to my tech.
I am on the fence about restoring it, I know the tuner section is not that good, but I have the 430 tuner, which it is excellent
 
It's a very good amp. If it's working, not too much to "restore". Just use the right bulbs, since using the wrong ones causes problems. The unit I've fixed was doing loud "bang" noises when changing the function selector, since somebody calcelled the muting circuit removing and disconnecting components, since the unit was muted due to the wrong bulbs used. I had to restore the muting circuit, and then trobleshoot the muting behavior until realized the main problem were the wrong bulbs.
 
Well, it’s a late 70s design, and except for the toroidal transformer, not really special sounding. At 105w/ch it can do some damage, but most of my other recievers spank it sound and feature wise. I have the 730 remote set, which is actually easier to use for volume control than the front panel capacitance buttons, which I had to clean internally to have easier operation (done at the same time I replaced some bulbs. ) Motorized pots in this design are clunky, for sure. Cute design, but stupid in many ways. The underside controls can only be seen at eye level and who has their receiver at eye level??
 
perryinva said:
In case anyone else comes across this thread, the function bulbs are standard #7219 bulbs from Mouser. They are soldered in. If you delete D311, the “mute on burnt out bulb” function is disabled. Because of the required current draw, LEDs can not be substituted. And don’t forget to replace the 4 AA cells underneath with lithium AA to prevent them from exploding. They make a heck of a mess if regular alkalines are left in there too long.
Click to expand...

What exactly do you mean with 4 aa cells? Are you implying that this receiver has built in batteries? I just purchased one but haven't taken a look at it yet, just waiting for the bulbs to arrive.
 
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