The Lets Track 9090DB/8080DB Production Changes Thread

[LBPete]

If you have been around the Sansui Forum for any length of time you know that the 9090DB and it's variants, the 8080DB, 990DB and 890DB are the topics in many threads. They are arguably the most popular and most widely produced of all Sansui Receivers. The earliest serial number we have on file is from September 1976 and the last one on file is from May 1978. During that time they were in almost continuous production. 10s of thousands of them were built.

Over that time span, Sansui made many production changes to these units. Some are minor or obvious like the position of the filter cap in the tuner power supply or the color of the plating on the chassis. Others are more involved or hard to see.

The serial number database is set up to track production changes. That would give us a better view of what we are getting. To do this we need to crowd source data, specifically the configuration of your unit. This information can be added to serial numbers that are already on file in the database or to newly added serial numbers but in every case there needs to be a valid serial number tied to this data.

Please keep in mind that not all modifications are factory modifications. Over the years many of these units have been modified by their owners. Ideally, we need the information from virgin units and we all know how rare an actual 40 year old virgin is.

Off the top of my head here are the production changes that come to mind. Please feel free to chime in with any that I missed.

Chassis plating, gold or silver?
F-2624 Driver Board bias control, cylindrical transistor or forked black diode?
F-2657 Protection Board, speaker protection fuses or no fuses?
F-2619 Tuner Power Supply Board, Filter Cap - Pointed straight up, laid over on it's side or underneath?
F-2656 Power Supply Board - R30/R31 - 1 ohm fuse resistors or actual glass fuses?

And last but not least, the Dolby Circuit:
Green flex PC board between F-2655 Dolby Board and F-2654 Push Switch Board or Black ribbon wire?
F-2655 Dolby Board - Rivets in pass throughs? These rivets are extremely hard to see and takes a trained eye to report accurately.

I'll try to put together pictures to illustrate each of these production changes.

I'm going to set up a companion thread in the Sansui Database Forum to post this information. That will keep it more viable so it doesn't get lost over time.

Here's a link to the tracking thread. Let the tracking begin!

- Pete

 

[Porkbuns]

Fun suggestion. Was really confused about the silver plated 9090 that I recently repaired since all the ones I've serviced had gold plating. I'll have to keep an eye on the serial numbers though because it's weird how many have come in that were very much around the same production run with similar boards etc.

 

[LBPete]

All 9090/8080s have silver plated chassis. Early production 9090DB/8080DB are silver as well. The plating change took place between April '77 and September '77. We need more data to get closer. The color of the chassis is important to this project because it's easy to see and may be an indicator of other changes that were made at the same time. From what I can tell, all gold chassis models have bias diodes on the driver boards but we don't know if they all had the ribbon cable instead of the earlier flex pc board in the Dolby circuit.

- Pete

 

[AlTinkster92]

Mines a late model 8080DB, will look for the things you asked for Pete, good thread!

 

[LBPete]

That first picture is the connections to the EQ board. All the X0X0DB models use flex pc boards in that location. Here are pictures of the early and late Dolby board.



The top picture is the later ribbon cable, the bottom picture is the older flex PC board.

Here's a picture of the later and earlier driver boards:


The board on the left is the later board with Bias Diodes, the board on the right is the earlier board with Bias Transistors.

- Pete

 

[Porkbuns]

Speaking of which pete, I'm in soCal area, we should meet up and talk audio.

 

[LBPete]

We are overdue for another SoCal AK Fest. We'll have to start looking around for a venue.

- Pete

 

[Porkbuns]

That would be awesome haha. There's actually a chance I may have run into you at one point.

 

[Dana65]

So which is better ? the older or the later one ? Can you replace the ribbon cable if it needs to be ? Is that something find or make up ?

 

[LBPete]

All things being equal, the later production is better. But all things are not equal. These units are nearly 50 years old and I would take a clean original early production over a thrashed late production any day. In other words condition is more important than production date.

- Pete

 

[Dana65]

Thank pete ! just what I needed to know

 

[Gary Sansui]

That first picture is the connections to the EQ board. All the X0X0DB models use flex pc boards in that location. Here are pictures of the early and late Dolby board.

View attachment 1249360 View attachment 1249361

The top picture is the later ribbon cable, the bottom picture is the older flex PC board.

Here's a picture of the later and earlier driver boards:
View attachment 1249365

The board on the left is the later board with Bias Diodes, the board on the right is the earlier board with Bias Transistors.

- Pete

Your black connecting tape version does not have the K terminal bypass. I have found this twice. I am Gary Sansui here on AK. Please if you have anything to add to my post, please do. I have had many questions about this I do not have the expertise to answer. F-2654/F-2655 Dolby modification post. And especially how to use this in other model years that did not have this bypass. I took some good pictures but I do not have the knowledge to answer any real questions.

thanks, Gary….sansuioldaudiophile

 

[LBPete]

I don't know what you mean by K terminal bypass. Please enlighten me.

- Pete

 

[SansuiSteve]

Big effort Pete, thanks for taking the lead. Will get mine opened up in the next month or so.....

 

[eiraved]

Your black connecting tape version does not have the K terminal bypass. I have found this twice. I am Gary Sansui here on AK. Please if you have anything to add to my post, please do. I have had many questions about this I do not have the expertise to answer. F-2654/F-2655 Dolby modification post. And especially how to use this in other model years that did not have this bypass. I took some good pictures but I do not have the knowledge to answer any real questions.

thanks, Gary….sansuioldaudiophile

I don't know what you mean by K terminal bypass. Please enlighten me.

- Pete

It appears @Gary Sansui posted pictures of this K terminal bypass on a separate thread.

Sansui F-2654/F-2655 DB Dolby circuit modification

There are several different modifications that Sansui made to this particular set of circuits. The model years with black connecting tape and steel FM/AM light reflectors have this K terminal modification. K terminal from calibration pots is not soldered to top traces on board there is a yellow...

audiokarma.org

 

[LBPete]

@eiraved, I never would have seen it there. Thanks for the link. It sounds like it bypasses some of the traces on the board but without digging into it I couldn't say for sure.

- Pete

 

[eiraved]

@eiraved, I never would have seen it there. Thanks for the link. It sounds like it bypasses some of the traces on the board but without digging into it I couldn't say for sure.

- Pete

It appears he posted it there after you asked the question. Not entirely sure why that happened, but I'm glad it was located.