This may be a question for Terry Smedley … or Norberto (?):
I’m going through and ordering parts to assemble the 4.0 Z80 board. from the comments in the BOM it appears that U113 (1.8432 Mhz full size oscillator) is not needed and can be omitted? The comment in the spreadsheet says “Replaced by 3.6864MHz Oscillator at U4”. Is this a rework of some kind? Odd that there’s a place on the final silkscreen for an oscillator that’s not needed?
Another question: I believe the 78L12 and 79L12 regulators provide the 12V signals for “true” RS-232 on the serial port. Will these work with a PC style power supply (i.e. if they have 12 V on the input side)?
Also as an FYI to anyone else who’s buying these parts: there’s a comment in the spreadsheet to buy the 16.384 MHz oscillator on Amazon but I’ll point out that Tayda also stocks this item.
https://www.taydaelectronics.com/crystal-oscillator-16-384-mhz.html
I’ve gotta think that’s a typo on the quantity in stock!?
On May 21, 2021, at 8:53 PM, norberto.collado koyado.com <norberto...@koyado.com> wrote:
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I believe U5 (ROM decoder) as well..?
Terry S/Norberto: shouldn’t that line in the BOM read as follows?:
U107,U5 NC-61 (PAL) 2 DIP20
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There are two GALs/PALs, but they are not both "NC-61". U5 is a RAM/ROM decoder and is programmed with something different. I'm not sure if they both use the same part, either.
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On May 26, 2021, at 8:30 AM, Terry Smedley <terry....@gmail.com> wrote:
Two GALs are needed, both can be same unprogrammed part number. F16V8BQL is the current Atmel part. Jameco still lists the equivalent, but discontinued, Lattice GAL16V8D. The programmer needs to know which part you are programming, but once programmed the two parts are equivalent in function.
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On May 27, 2021, at 2:07 PM, Gery Kissel <gkisselsp...@gmail.com> wrote:
I plan to go old school on this and use the 7805 regulators. What is the recommended heat sink method? Heat sinks are not accounted for on the BOM.
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On May 27, 2021, at 8:49 PM, norberto.collado koyado.com <norberto...@koyado.com> wrote:
I will send you the correct picture once I get home.
From: se...@googlegroups.com <se...@googlegroups.com> on behalf of Steven Feinsmith <steven.f...@gmail.com>
Sent: Thursday, May 27, 2021 5:44 PM
To: se...@googlegroups.com <se...@googlegroups.com>
Subject: Re: [sebhc] Z80 Rev 4.0 board BOM
I looked at the picture. The voltage regulators are mounted outside from the board via a bracket.
It will be better to mount the opposite side. The wires will not have to cross the metal edge. The short length of the wire is better than the long one.
The best way is to have the voltage regulators mount on the PCB and put the heatsink compound to mount on metal brackets to distribute the heat.
Steven
Yes, the mounting bracket which is used as a heatsink as well for the LM7805. If you need another one, I can send you one.
This is how it should be mounted (guideline): Or you can follow Heath latest info on how to mount them.
This board support the flat mounting bracket to avoid soldering cables to the LM7805 and just solder the 7805 directly to the board and use the mounting screws to hold the regulator in place. I prefer this method better.
<image.png>
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On May 27, 2021, at 6:35 PM, Terry Smedley <terry....@gmail.com> wrote:
This is the method that Norberto suggests. It utilizes a flat mounting bracket. The regulator can be mounted to the bracket/heat sink and the leads soldered directly to the board with no connectors or wires. As Glenn noted, the 3-position connector that Heath used was prone to developing resistance over time.
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<H8HeatSink2.jpg><H8HeatSink1.jpg>
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The substitute for the RTC-72421 is the surface mount RTC-72423. I will need to develop an 18 Pin to 24 pin breakout board. The pcb can install the surface mount part as my eyes are not that good anymore.
Something similar to this:
On the 74HCT parts, they can be substitute with 74ALS, 74F, or 74LS as needed. You can check this website as well: https://www.futurlec.com/IC74Series.shtml
For the 5-pin position you can order form amazon: https://www.amazon.com/dp/B01M69TKAM?psc=1&ref=ppx_yo2_dt_b_product_details as the other connectors are used across other boards and on the backplane.
Norby
From: se...@googlegroups.com <se...@googlegroups.com> On Behalf Of Peter Higgins
Sent: Friday, July 23, 2021 9:47 AM
To: SEBHC <se...@googlegroups.com>
Subject: Re: [sebhc] Z80 Rev 4.0 board BOM
Some updates to the BOM for this board:
1. The 72421 RTC (U103) is an obsolete part that Mouser (listed as the sole source in the BOM) no longer has in stock. It is also no longer available from DigiKey, and the usual sources of obscure and/or obsolete parts (like Unicorn and Anchor) do not have it. It seems the only remaining source is eBay.
2. The 5 position header for connection to the front panel (P201) is also an obsolete part no longer available from the listed sources (Jameco and Mouser). With an internet search one can find a few places still selling it, but you might end up paying $20 or more in shipping to acquire just this one $0.35 part.
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