Alternator out warning board
 

Hi all
Could anybody send me the p/n for the alternator warning board on the top front firewall F337G '75. This one has got badly corroded and in need of replacement.

Thanks

Pete

Need Picture...
 

Pete,
Can you post a picture of the part that you need the number for?
guy, the old 72 driver...

Hi Guy
I have not got a picture of the board, but it is the one on the top middle of the front engine firewall, with the big diodes and 2 fuses mounted on it. And a terminal block at the bottom. It controls the alternator out lights. I have a circuit diagram but no parts list, and this one is BER.
Many thanks for your help.

Pete

There is an alternative to getting a new circuit board. You can replace the board with an STC'd replacement from Elecronics International that will give you a digital volt meter/ammeter. I am getting ready to do this during my annual starting in a couple of weeks.

Mark

Thanks Mark

Could you send me the address and email if poss so i can get and idea of the cost.
Problem is the Skymaster is UK reg so it is geting passed the CAA, however if there is a STC that would make it easier.

Many thanks for your help
Regards

Pete

Replacement VA from EI
 

Peter:

You want to use the VA-1Axx unit from Electronics International. The xx indicates the size of the shunts needed, which depends on which alternators you have. You can see the unit at http://www.buy-ei.com/VA-1A.htm . List price is $342 (USD). You also need a switch RSVA-3 so that you can monitor each engine on the single instrument. List price for the switch is $98 (USD). You also need two shunts. The S-50 shunts are rated for 50 Amps, and their price is $35 (USD) each.

Hope this helps.

Mark

Guys,

In aviation, as in most things, there are always multiple opinions. Mine is different from Mark's, and I offer it here for you to consider.

I had the EI volt/ammeter in my P337, along with the switch and the shunts, and like Mark, I think it is an excellent unit. In fact, I would not own a 337 without putting one in, because the electrical system is the weakest system in Skymasters.

That said, I did not, and would not, replace the overvoltage board you are talking about with this meter. I would have the meter *in addition to* the board. I am very uncertain that installing the EI VA meter actually can be used to replace the board, but I will take Mark's word for that. I thought the meter was STC'd to replace the Cessna ammeter. But anyway, here is why I would not replace the board with the EI meter:

If you wire around the board we are talking about, you lose, at least, your red overvoltage, red discharge and yellow "alternator out" lights. The EI meter provides a discharge light and an overvoltage light only. The problem here is that if you lose a single alternator, and you have only the EI gauge, you will have no immediate indication that anything is wrong. In fact, the only way you can detect the loss is to switch the EI guage from the left to the right alternator, and look at the current being produced by each. If the EI gauge shows zero for one alternator, then you would know that the alternator selected has stopped producing current (which may or may not mean you have an alternator problem, but that is a whole 'nother story).

If I am flying IFR on a dark and stormy night, I want to know *immediately* when one of my alternators fails. I have had exactly this experience on my '65 337 when the alternator shaft coupling failed. And I would find it a pain in the butt to have to train myself to check the alternators every X minutes by flipping the switch.

So my recommendation, for what it is worth, is to install the EI VA meter, because it is so helpful in diagnosing electrical system problems. But also, I suggest you repair or replace your warning light circuit board, because it provides an important function as well.

My two cents, worth what you paid for it.

What problem are you having with the board that leads you to want to replace it? Have you thought about having your avionics shop take a look at the board, see if can be repaired?

Kevin

Kevin:

You've given me something to think about. I was told by somebody at CPA that the STC would allow me to remove the circuit board we are discussing. Now, I am wondering if that is true, or if the STC only allows replacing the Cessna ammeter (which I don't have in the first place). And I am intrigued by your thoughts on having both, although the diodes and capacitors on the circuit board are a source of continuous maintenance. I'll have to think about this.

When you put in the EI VA, where did you locate it if you left in the original circuit board?

Thanks

Mark

The meter went in the instrument panel, as did the switch (well, you asked ;-). The actual indicator went on the co-pilot instrument panel in the hole where the Cessna EGT used to be, to the right of the fuel flow indicator and just above the copilot control wheel. The switch went below the cowl flap switches. I will attach a picture in the next message (not this one), you can see the switch on the lower left, and a small slice of the voltammeter on the far right. I will attach another picture in the next message after that showing the volt ammeter better.

The shunts went on the left (pilot's) side of the firewall in the engine compartment. I can't remember, but they were fairly high up, fairly accessible from above.

The board is undoubtedly a pain. I think I had to mess with it to fix it at least three times in five years. One of those times I think we replaced it, and at that time, while not cheap, it was not crushingly expensive either as I recall. But maybe time heals financial wounds...

Kevin

Center instrument panel.

right panel.

One more point, you can see in the second picture that the plastic around the gauge has been reshaped with a heat gun. This was done to make the discharge warning light on the guage visible from the pilot's seat. Without the reshape, the plastic covered the pilot's sight line to the warning light.

Kevin

Thanks Kevin. That is very helpful.

Mark

Thanks Kevin and Mark

Kevin the printed cicuit board has suffered from the best of English weather and is very corroded, i have repaired it many times and it is now beyond repair.
So i am looking for a part number for a new PC board (if they are still avialable).

We were just discussing the point you made about the ALT out lights, and you are quite right i would not be happy without these lights, if an alternator went out you need to know.

So it is back to the PC board, if anyone could help with a p/n for the complete assy i would be grateful.

Thanks for the pictures Kevin.

Regards
Pete

Sorry Pete, I gave my parts and service manuals to the new owner of my airplane when I sold it (sound of grown man crying). I hope someone else on the site can look up the part number for you for your '75 F337G.

Kevin

Peter:

I'll look it up tonight, and post it for you, assuming the4 part number for a '73 P model is the same as for yur aircraft.

Mark

Pete,

I found the alternator warning board in my maintenance records. I have a part number of 1570059-1 on a '73 P337. Cost was $965 in 2001. Don't know if that will help, and I can do nothing to verify the part number.

Good luck,

Kevin

Kevin and Peter:

The way I interpret my drawings and service manual, the part number that Kevin refers to, 1570059-1 is just for the diode assembly (diode and heat sink). If I am right, you can buy the diode from Radio Shack or Newark electronics for less than $75. This is what I did when I had to replace my diodes, thanks to advice from GMAS. The price I got at the time from Cessna was about $750 (can you believe it?).

I think the part number for the circuit board assembly is actually 1570304-1, based on the schematic drawing. I have no idea if by the word "assembly" they mean that there are other components mounted on the board, or if it is just a circuit board. The drawing isn't very clear to me, but this part number is the only part referred to as a circuit board assembly on the drawing which shows the alternator wiring diagram.

Perhaps with these two part numbers you can call a Cessna dealer and at least find out which of these part numbers (if any) is correct.

Sorry to not be more sure of my answer, but hopefully this is a starting point for you.

Mark

I have some advice on the printed circuit board, but let me first make an observation. As an aerospace engineer on my second Skymaster, I have been following this thread with considerable interest because of its insightful content. Especially the two comments from Kevin: first, that the original warning lights are too important to discard, and second, his theme (to which I'll add a little spin) that the electrical system is too complex and too weak for us to be modifying it.

My main suggestion to Peter is that the printed circuit board and other components which you are seeking might be found in good condition -- and at huge savings -- from parted-out Skymasters which spent most of their life in arid regions. The "Purchasing Parts" page of my Skymaster website at www.SkymasterUS.com gives detailed directions on buying used parts successfully and provides the names and contact info of suppliers. I would start with Don Nieser at Commodore.

Also, to make sure that you have the right part numbers, you may need the aircraft serial number; this is particularly true if yours is a French-built Skymaster. Finally, the optimum approach is for you (not someone else) to look at the Illustrated Parts Catalog, so that you can choose from the illustration all of the parts you need and their part numbers, and to make sure that those part numbers apply to your aircraft serial number.

Ernie

Pete,

I also installed an EI-VA1 volt-ammeter with the three-way switch for front, rear and battery current. I left the factory warning circuitry in place. I happen to have a picture of the shunt installation that I took when the front engine was out for replacement recently. You can see that I installed the shunts by stacking the front regulator on top of the rear regulator with spacers for cooling. I then made an aluminum plate with mounting holes that matched the regulator and attached the three shunts. I then built a bracket to hold the 6 required fuses.

My skymaster has de-ice boots, making firewall real estate very valuable. This was about the best layout I could come up with.

David

I added a quad gauge that includes Volts, Battery amp draw, Front alt output, and rear output. Giving you a visual without having to flip switches.

Thanks everyone

I did not expect that amount of replies!!

The concusion it that-
Although installing the EI type indicator eliminates the ammeter, there does not seem to be a mod to get rid of that PC board and the troublesome relays, ah well never mind i will try and get a new or used unit. Well it did give Mark something to think about!!!

I will try your site Ernie, thanks.
The 337 electrical system is very easy, the main problem is people think is complex, as an (out fo work) Avionics eng with 30 years experiance and the Cessna courses (including 337 electrics) i have a little head start.

I will have to think about a unit that will replace the ALT out board at a later date.


Again many thanks
Peter

I've always wondered, what would be the problem with running each alt. on it's own regulator?

Richard.

On the models 337G and above they do run separate regs for each alt, but not on your 337B.


Peter

Alternator board
 

The PN on my 73 337G is:
1570057-1 Rev A

over & under voltage sensing assembly
 

my parts catalog for '73-'80 P models shows part no. C593004-0101 for the description "sensing assembly-over & under voltage". To me it's not clear if this is for the circuit board or not. I have left the warning lights "dumby lights" and added the EI volt/amp meter for trouble shooting. I had rebuilt the warning board by replacing all the electrical components and attched a diagram with part numbers for the diodes and relays to an earlier post.
Dan
________
Buy Vaporizer

Reed Relay
 

Hello all, does anyone have a current part number for the(2)REED RELAYs as shown on the "Schematic Alternator Warning" wiring diagram, drawing# 1571000 in the service manual? The part numbers (PN300-884-9944) on my relays are now obsolete.

I have called Don Nieser and several other sources without success so any help/ideas would be a greatly appricated.

Thank you,

BK

I think the unit you are looking for is 1570058-1 (Figure 134 of the IPC, 73-80). Cessna has 5 of them, $1423 ea.

Thank you for the info.

alternator warning control board
 

I rebuilt the entire board on my '77 NA G model, and replaced the reed relays with new from the manufacturer, Computer Components Inc.
1-800-653-9909 Part#300-884 (x2). ($75 each, plus $17 shipping).
www.relays-unlimited.com

If you're going that far, recommend replacing the diodes and resistors too.
There are a couple posts in the forum discussing the modern equivalent part numbers and sources.

Learjetter,

I placed an order with Computer Components but they only had 1 in stock with a 3 month wait for the second relay. I searched the web and found another for $225.00 along the 4 resisters at Wilco.

Long story, but I also found a new surplus PC board for $175.00. After finding the board, I decided to make up a new unit and ordered all new diodes and the MS terminal boards.

The only 2 items that I could not get in the correct part numbers were the fuse blocks and 7 position bottom terminal strip and, according to Cessna, they are no longer offered. That said, I found similar components with the same ratings and also have them on the way.

I should have less than $700.00 total in parts for a new board. New surplus and "as removed boards" were running from $2,600.00 to $4,100.00 so, I'll have some fun and save a few coins.

If you could post a photo of your board it would be great and thank you,

BK

This is incredibly useful info, thanks all. I'll likely need to do this on my 73G restoration. Would anyone be interested in an aftermarket cover for this unit? My cover is missing and I'll probably need to get some metal bent for it...may as well make a few.

When you found this board, was there a part number associated with it? I am in the process of rebuilding mine. Thanks

I have attached a list of the components, part numbers and vendors I used to replace my assembly and so far, the Alt Out warning light hasn't been flashing.

Control Board
 

Thanks you for posting that information. I bought the 300-884 Relays a couple of months ago and they actually arrived yesterday. I bought the rectifiers and some diodes. I will use your list to collect the rest.

I have been thinking about why there would be so much trouble with these alternator lights if both regulators are set to the same voltage, either 27.7 or 28.8 volts. One possible area for this is since these are not paralleled in real time by the regulators, there is potential voltage drop from the rear to the front, thereby the incoming voltage from the rear would then be less that from the front. Just spitballing.

You hit the nail on the head. You can install my 400-Series voltage regulator upgrade, and in all cases so far, the flashing alternator lights stay dark. Adding true paralleling alternators equalizes the load between front and rear.

I'm not clear what Cessna engineers were thinking when they designed the Skymaster's voltage regulation system, but it may have to do with the fact that the engineers at Pawnee (Cessna's single engine factory) had never built a twin before (and would never build another).

Alternator Warning System
 

Getting close to having my bird in the air. Been working on my Alternator warning system. Neither alt light would come on. My parts airplane, N3CY, had a AMF Portter Brumfield JRE1AD1 24v 10a reed relay on the board for the front alternator. While waiting for my 300-884 relays from computer components I acquired a number of the JRE1AD1 relays and installed them as depicted in the photo for the front and rear.

The front alt out light immediately worked rear did not. After hours of looking at the manuals, trying this and that, could not figure out why the rear large diode had battery voltage on both sides. The front alternator only had 5 volts on the anode side and the rear diode had 24 volts on the anode side with no alt light on the panel. Finally after looking at the tracks on the back of the pc board, where the relays are soldered in use opposite sides of the relays for the front compared to the rear. I unsoldered the rear relay repositioned it back in with the lettering upside down, and now I get 5 volts on the anode just like the front and the rear alt light is now on. Using a bright lite to light up the photocell on the panel increases the intensity of the alt lights making them easier to see. What a PINA.

Front alternator reed relay shown in pic.

Now to get my starter adapter back together to see if the lights go out with the alternators running.

Dan
67S

Received my 300-884 reed relays Thursday from Computer components, I bought 4 at 90.00 each, about six weeks wait. Installed one for the rear alternator, right side of board, it all works fine now with the AMF relay installed on the left side.