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Fixed Bad 512K VRAM in my LC II !

Verault

Well-known member
One of my only 512KB VRAM modules I own thats in my LC II went bad this year or last:IMG_20211023_122814.jpg

I bought 4 of the exact same type of

TC524258BJ-10 Ram Chips online.​

IMG_20211023_122838.jpg
I ended up using 3 of the 4 chips I purchased. I have a feeling one of them may not have been bad but a bad contact. I marked them and saved them for a future issue.

Video is clean and clear now!
IMG_20211023_132802.jpg

This LC II is done!

Hoping you guys can help on another issue. I made the bonehead mistake of hot plugging a scsi device into my Original LC and now the SCSI BUS is dead. It wont detect anything and just skips past to the floppy drive blinking icon. I know the chip at UE9 is an AMD AM85C80-8JC
I cant seem to find a replacement online for this chip. Any of you know where I can purchase a replacement?
IMG_20211023_134518.jpg
 
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joshc

Well-known member
The exact chip is available on utsource: https://utsource.net/sch/AM85C80-8JC.html

Alternatively, I think that can probably be replaced with something similar - though I don't know exactly what, but as it's a SCSI microcontroller I think some of these are still made and they may have a compatible pinout?
 

Verault

Well-known member
Thanks Josh. I have been a little off put by UTsouce needing an account before being able to request or purchase anything. Have you or anyone else ever actually purchased from them before? I have purchased plenty from Jameco, Grainger, Mouser, and digikey... But not Utsource. I just want to make sure they are on the level.
 

Verault

Well-known member
Ok I guess it certainly worth a try as they are the only people to stock the exact part. Thanks Josh.
 

Siliconinsider

Well-known member
I have purchased some ARM710 from UTSource, they came new and top notch. The important thing to know about them is that they don't have stock, they are a broker that list stock from various (mostly chinese) sellers, and your mileage may vary. Some parts they claim to have are not in stock, you may receive used or remarked parts as well as it is common on the chinese market. UTSource acts as an escrow system that checks the quality of the goods upon receiving them from the place that actually has the stock and forward them to you, and handle the payment.
 

Siliconinsider

Well-known member
M
Yes, more than a storefront, as the parts are actually inspected and going through UTSource physically, but you got the idea.
 

trag

Well-known member
The exact chip is available on utsource: https://utsource.net/sch/AM85C80-8JC.html

I wouldn't count on Utsource actually having anything at a given price without an explicit quote from them.

I put together a ~$900 order of various parts, including a few I got quotes on, and got back so many "Oh, we don't actually have that" (for parts that claim 33000 in stock) and "the price is now five times what we advertise", that I cancelled the whole order as a bad Bait and Switch swindle.

I would be interested in reading a narrative of how some of our members conducted successful orders. Perhaps entirely by phone? For example, the SWIM chips that Kai obtained, when I requested a quote for them, they are now asking $110 each with a 100 qty minimum.

After ordering the RTC and ADB chips which are listed on their website, they came back and said they didn't have any.

They do seem to have the sound chips for the SE/30 for $1.75 each, minimum 100, as I got an actual quote on those.

Alternatively, I think that can probably be replaced with something similar - though I don't know exactly what, but as it's a SCSI microcontroller I think some of these are still made and they may have a compatible pinout?

The 85C80 is a combined SCSI/SCC chip. It includes the functionality of the 53C80 SCSI chip and the 85C30 serial chip. It's going to be a lot harder to find than the individual chips, I think.

Although, questcomp.com lists them as in stock also. They have a price listed on the 100 pin QFP. but the 68 pin PLCC is all, request quote. Might be worth the effort. I've had successful, non-irritating, orders from questcomp.

AMD made a variety of these combo chips culminating in the 79C950, which combined a 53C96 SCSI chip, 85C30 SCC chip and some form of Ethernet chip (10 Mbps).

Some of the PowerBooks used combo chips to save room. I didn't realize that extended to the LC and LCII until I checked the developer note just now.

The Quadras have distinct chips (except the AV models, which use the 79C950).
 

Attachments

  • AM85C80.pdf
    4.5 MB · Views: 4

Siliconinsider

Well-known member
The ARM710 I ordered straight from the website and they were brand new in trays, but the ARM60 were "sorry we don't hold stock". This is when they ask the actual seller that listed them. I had good hope with the ARM710 as this is not something in high demand at all, so there's no incentive to fake it.

Knowing how the chinese semiconductor market works, most listings are placeholders to attract attention without actual stock. Parts that are in high demand within the retro computing community or that are specific to a machine will have a a very high chance of being recycled and/or laser remarked. And the price is most of the time never right, it is more expensive, especially after someone orders that part.
 

joshc

Well-known member
The 85C80 is a combined SCSI/SCC chip. It includes the functionality of the 53C80 SCSI chip and the 85C30 serial chip. It's going to be a lot harder to find than the individual chips, I think.

Good to know, thanks for the clarification.
 

trag

Well-known member
From the "Connection Diagram (page 3-7) in the datasheet, it appears that if one wanted to, one could just wire separate 53C80s and 85C30s together and get the same functionality. Better if you can find the already combine chip, though.
 

Verault

Well-known member
The bottom two thirds? Why does it have two 85C30 Serial Chips in one? What is the benefit of that?

Trag I bit the bullet and purchased 4 of the AM85C80-8JC. Lets see how that goes and what the time to delivery may be. Says almost 2300 in stock so who knows.
 
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Siliconinsider

Well-known member
The 85C30 is a dual interface chip. The best way to do it is to grab some samples from different sources and see what you get before ordering a larger quantity (should you need more). I can't think of any use of the 85C80 outside of macs, but it should still be a standard part from the AMD catalog.
 

Verault

Well-known member
I paid via paypal so if there is an issue I am confident in thier dispute process. And I own maybe 8 Macintosh LC's. But I know, there is always a risk. I am no stranger to buying chips that dont fix the issue.
 

trag

Well-known member
The bottom two thirds? Why does it have two 85C30 Serial Chips in one? What is the benefit of that?

Trag I bit the bullet and purchased 4 of the AM85C80-8JC. Lets see how that goes and what the time to delivery may be. Says almost 2300 in stock so who knows.
Did you just place an order on their website, or did you talk to someone about pricing and availability?

Please let us know how it turns out. Curious to see if they actually honor this posted price.
 

Verault

Well-known member
I just selected the quantity I wanted and went through the checkout process.. As I would do on any other website. If I did something wrong in the process I would say the interface is very counter intuitive. Yes I will let everyone know how it turns out. So far all I received was a notification from paypal that I paid them with the recipients info being "You sent a payment of $18.81 USD to 创新无限信息技术(武汉)有限公司 (whfmco@hotmail.com)" as well as a UTsource confirmation for a paid Purchase order with corresponding number.
 

MrFahrenheit

Well-known member
Did you just place an order on their website, or did you talk to someone about pricing and availability?

Please let us know how it turns out. Curious to see if they actually honor this posted price.

I just ordered from UTSource for the first time a few weeks ago. I purchased VRAM chips. I was advised to inquire for a quote, as the price may be less. I got the quote and it was $0.05 more than the advertised price on the site. I accidentally somehow placed that order instead of placing an order for the chips on the site at $0.05 less. Oops. Then I found out it was from a particular supplier, and I wanted to ensure I would get the chips I needed, so I placed a standard online order (no price inquiry/quote). I got that order before the first one. I ended up with both orders.

Then, last week, I decided I needed a few more chips, and placed another order (with a 15% off coupon from them) and a day later they told me they only had 1/2 the chips I ordered, and were refunding the rest. But they still charged me the full shipping amount, it should have been at least $10-15 less for the shipping.

Someone over at TD bought some 68030 50mhz CPUs from UTSource, and received fakes. So your mileage WILL vary.
 
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